how to calculate months with a due date in vb 6

Dim dateprev, datelast As Date dateprev = Format(txttrandateprev.Text, "mm/dd/yy") datelast = Format(txttransdatelast.Text, "mm/dd/yy") txtmonths.Text = DateDiff("m", dateprev, datelast) exam txttrandateprev.Text = "09/11/11" txtransdatelast.text = "10/10/11" wrong answer txtmonths.Text = "1" correct answer txtmonths.Text = "0" due day is 11 and the last trasaction day 10 is not greater than the due 11 anyone can help me please!!!