This example adds a text form field named "Today" at the beginning of the active document. The EditType method is used to set the type to wdCurrentDateText and set the date format to "M/d/yy."
With ActiveDocument.FormFields.Add _
(Range:=ActiveDocument.Range(0, 0), _
Type:=wdFieldFormTextInput)
.Name = "Today"
.TextInput.EditType Type:=wdCurrentDateText, _
Format:="M/d/yy", Enabled:=False
End With