I'm thinking you need to convert the word constants into their integer values
wdAlignTabCenter = 1
wdAlignTabRight = 2
wdTabLeaderSpaces = 0
Code:
'So try changing this line
rng.ParagraphFormat.TabStops.Add Position:=InchesToPoints(3.25), Alignment:=wdAlignTabCenter, Leader:=wdTabLeaderSpaces
'to
rng.ParagraphFormat.TabStops.Add Position:=InchesToPoints(3.25), Alignment:=1, Leader:=0