thanks everyone, but now I have a new problem.. this program I'm making runs in the background (with me.hide), so sendkeys wouldn't work..

I searched the forum and found some code but can't get it to work

Code:
Private Sub Timer1_Timer()
  opendialog = FindWindow(vbNullString, "Choose file")
  If opendialog > 0 Then
    hEdit = FindWindowEx(opendialog, 0&, "Edit", vbNullString)
    Call SendMessage(hEdit, WM_SETTEXT, 0&, "C:\test.txt")
    Timer1.Enabled = False
  End If
End Sub
I also downloaded winspy++ to check if the name of the editbox was "Edit" and I'm pretty sure it is