Therefore it needs to be in a new thread. How can I send information from
the main apps functions to the thread so it can write to the log file. I do
not want to create a thread everytime the user performs a function I would
like to create 1 thread when the app starts and just pass information to it.

EG..

User starts application, the logging thread is created, from here on out
everything done in the main application is sent to the logging thread. When
the user click a command button it would pass "frmMain, function
'OpenStaff', cmdOpen CLICKED" and the logging thread would recieve this text
and write to the log file.

this is the structure i could use to solve your problem:

1. program starts from <sub Main>
2. the user form object is <UserForm>
3. <LogCommandID> is the integer variable we are using to pass log commands.
You set this variable to a non-zero value when user interacts with UserForm
(through command buttons or something)
4. <AppendToLog(LogCommandID%)> is the procedure to printout your log data

Public LogCommandID%

Sub Main
   LogCommandID = 0
   UserForm.Show                     (=NOT modal, execution continues)
   Do
       If (LogCommandID=0) Then
          DoEvents
       Else
          AppendToLog(LogCommandID)
          LogCommandID = 0
       End If
   Loop
End Sub

Dont forget to end the program through the Unload event of UserForm (or put
a control variable to the Do..Loop)