You can change the default printer for your application using Printer object and Printers collection. Here is example from MSDN:

<B>
The Printers collection enables you to query the available printers so you can specify a default printer for your application. For example, you may want to find out which of the available printers uses a specific printer driver. The following code searches all available printers to locate the first printer with its page orientation set to Portrait, then sets it as the default printer:

Dim X As Printer
For Each X In Printers
   If X.Orientation = vbPRORPortrait Then
      ' Set printer as system default.
      Set Printer = X
      ' Stop looking for a printer.
      Exit For
   End If
Next
</B>

For more information see "Printer Object, Printers Collection" topic in MSDN.