I had a hard time figuring out how to use Parameters.Refresh with
Oracle and ADO 2.6 (provider = msadora.1), so I thought I'd post the
solution I came up with here:

  Set ocmd = New ADODB.Command

  With ocmd
    Set .ActiveConnection = moConn
    .CommandText = "{CALL myPackage.mySp(?)}"
    .CommandType = adCmdText
    .Parameters.Refresh
  End With

  I found after doing this I could inspect the Parameters collection
and see all the parameters defined.  My initial testing also shows you
_don't_ have to supply a "?" for each parameter.  I've tested this
with an SP with five parameters, and it added all five parameters to
my Parameters collection even though I only passed the one "?".

  The wisdom in using Parameters.Refresh has been discussed ad nauseum
on Usenet.  For what I needed to do it was the logical approach.  In
an SP where the parameter count and types are unchanging,
Parameters.Refresh wouldn't be a wise thing to do.