You didn't say what version of winword or delphi and the answer
varies.

Word 8
Application.Dialogs(wdDialogFilePrint).execute
or
MyDialog := Application.Dialogs(88);
MyDialog.execute;

Or even
Application.ActivePrinter := "Printer on Port";

Word 7 - you can do it in a called macro
(syntax not guaranteed)

myobject.call("template.macro");

macro
Dim mydialog as FilePrint
GetCurValues mydialog
Dialog mydialog
FilePrint = mydialog

or
wordbasic.fileprintsetup([.Printer="Printer on Port",
DonotsetasSysDefault=1])