hi Jeff,
i am not realy sure, what you like to do, but if i understand you right something like this should work:
lets say you like to modify OEMdro2000 and you hit the "key" 1 on your virtual Keyboard the VBmakro for KEY1 could
be something like this:
Sub Main
  ActValue = GetOEMDro(2000)
  If ((ActValue  <= 9) AND (ActValue  > 0)) Then
    ActValue = ActValue * 10
    GoTo write
  End If
  If ((ActValue  <= 99) AND (ActValue  > 0)) Then
    ActValue = ActValue * 100
    GoTo write
  End If
  If ((ActValue  <= 999) AND (ActValue  > 0)) Then
    ActValue = ActValue * 1000
    GoTo write
  End If
  If ((ActValue  <= 9999) AND (ActValue  > 0)) Then
    ActValue = ActValue * 10000
    GoTo write
  End If
  If ((ActValue  <= 99999) AND (ActValue  > 0)) Then
    ActValue = ActValue * 100000
    GoTo write
  End If
write: ActValue=ActValue+1 'Key 1 was pressed 
SetOEMDro(2000,ActValue)
End sub 
code not tested, just written down.
Thomas