This is what I want to do:
This code is run from an Access form.
Use the VBA Find method to see if this contact is already
in the folder. I can use the Email address plus the name
as the criteria.
If found, ask the user if the contact is to be update with
information from the current Access form.
I need to know how to update the found record.
If not found, create a new contact item. I know how to do
this.

Setting properties in an Outlook item is simple. Once you have the item (objContact):

    objContact.prop = "whatever" ' for builtin properties
    objContact.UserProperties("prop") = "whatever" for custom properties

then

    objContact.Save

See http://www.slipstick.com/dev/propsyntax.htm for more information on Outlook property syntax.
--
Sue Mosher, Outlook MVP
Outlook and Exchange solutions at http://www.slipstick.com
Author of
     Microsoft Outlook Programming: Jumpstart
     for Administrators, Power Users, and Developers
     http://www.slipstick.com/books/jumpstart.htm

What do I Dim objContact as? I presume a ContactItem.
The help files on Find don't make it clear what to Dim a
variable.

Is this code on the right track?
Set objContact = MyFolder.Items.Find(".........")
If Not objContact Is Nothing Then
'Update the properties
objContact.BusinessAddress = Me.txtAddress
objContact.Save
....
else
.....
End If

There are some properties you can't do a Find on, like
EmailAddress, is that correct?
What does SetColumns do and is it useful in this case?

have the item (objContact):
information on Outlook property syntax.

That's because it depends on the context in which you are using Find. You can always use Object. If you are searching a contacts folder for a contact-specific property, then you could use Outlook.ContactItem. (Remember that contacts folders may also contain distribution lists.)

Yes, that's on the right track. See http://www.slipstick.com/dev/finddate.htm for some general pointers on building and using Find strings, mixed in with the specifics about date search strings.

The Help topic on Find covers this.

It caches the Outlook properties that you specify. It can speed up performance when you need to work with a bunch of items and only built-in properties. Since you're looking for just one item, it's not relevant here.

I solved it like this. The user wants to put the
information into a specific folder. The Find method does
work on the Email1Address property.

Private Sub cmdOutlook_Click()
On Error GoTo EH

 Dim objContactItem As ContactItem
 Dim objFolder As Outlook.MAPIFolder
 Dim objFolderLevel1 As Outlook.MAPIFolder

   Set olkApp = New Outlook.Application
   Set olkNameSpace = olkApp.GetNamespace("MAPI")

   Set objFolderLevel1 = olkNameSpace.GetDefaultFolder
(olFolderContacts)
   Set objFolder = objFolderLevel1.Folders("EventContacts")

   If IsNull(Me.Adressedemessagerie) Then
        Set objContactItem = objFolder.Items.Find
("[Categories] =""" & "EventsContact" & CStr(Me.ID) & """")
   Else
        Set objContactItem = objFolder.Items.Find
("[Email1Address] =""" & Me.Adressedemessagerie & """")
   End If
   If objContactItem Is Nothing Then
    '-- Create an Outlook contact entry

       'Set objContactItem = olkApp.CreateItem
(olContactItem)
       Set objContactItem = objFolder.Items.Add
(olContactItem)
   End If
     With objContactItem
      .FullName = Me.Prnom & " " & Me.Nom
      .FirstName = Me.Prnom
      .LastName = Me.Nom
      .BusinessAddress = Me.Ruedomicile
      .BusinessAddressCity = Me.Villedomicile
      .BusinessAddressPostalCode = Me.Codepostaldomicile
      .BusinessTelephoneNumber = Me.Tlphonedomicile
      .BusinessFaxNumber = IIf(IsNull
(Me.Tlcopiebureau), "", Me.Tlcopiebureau)
      .HomeFaxNumber = IIf(IsNull(Me.Tlcopiedomicile), "",
Me.Tlcopiedomicile)
      .Email1Address = IIf(IsNull
(Me.Adressedemessagerie), "", Me.Adressedemessagerie)

      '-- This helps to know this Outlook contact came
from Access
      .Categories = "EventsContact" & CStr(Me.ID)
      .Save

    End With

   Set objContactItem = Nothing
   Set olkNameSpace = Nothing
   Set olkApp = Nothing
EH:
If Err = 94 Then
    Resume Next
Else
    If Err > 0 Then MsgBox Err.Number & " " &
Err.Description
End If
End Sub

This is to send a event booking to the calendar.
There is a problem with the Start property, because the
date and time fields are separate text boxes on this
Access form, and I am not sure how to concantenate the
strings to place in the Start property.

Private Sub cmdOutlookAppointment_Click()
On Error GoTo EH
   Dim olkApp As New Outlook.Application
   Dim olkCalendar As Outlook.MAPIFolder
   Dim olkNameSpace As Outlook.NameSpace
   Dim objAppointmentItem As AppointmentItem

   Set olkNameSpace = olkApp.GetNamespace("MAPI")
   Set olkCalendar = olkNameSpace.GetDefaultFolder
(olFolderCalendar)

   Set objAppointmentItem = olkCalendar.Items.Find
("[Categories] = """ & CStr(Me.EventID) & """")
   If objAppointmentItem Is Nothing Then
       Set objAppointmentItem = olkApp.CreateItem
(olAppointmentItem)
   End If
   With objAppointmentItem
        .Categories = Me.EventID
        .Subject = Me.EventType & " " & Me.ClientID.Column
(1)
        .Start = CVDate(Me.Event_Date)
        If Me.Location.Column(1) = "Residence" Then
            .Location = Me.txtRue
        Else
            .Location = Me.Location.Column(1)
        End If
        .Save
   End With

EH:
If Err > 0 Then
    If Err = 94 Then
        Resume Next
    Else
        MsgBox Err.Number & " " & Err.Description
    End If
End If
End Sub

using Find. You can always use Object. If you are
searching a contacts folder for a contact-specific
property, then you could use Outlook.ContactItem.
(Remember that contacts folders may also contain
distribution lists.)
http://www.slipstick.com/dev/finddate.htm for some general
pointers on building and using Find strings, mixed in with
the specifics about date search strings.
speed up performance when you need to work with a bunch of
items and only built-in properties. Since you're looking
for just one item, it's not relevant here.

Depending on exactly how you have the Access form set up, you might just concatenate the strings, then use CDate:

objAppointmentItem.Start = CDate(Me.DateBox & " " & Me.TimeBox)