commondialog.showprinter

Hi
I had 2 points on the the pages input box
1. what if user enters a less than zero number
it seem that there is a built in function to stop this

2. I only want the user to print single pages not a range
how to control this as when I test the input CDC.FromPage
only seems to have a single number even when I enter a range
like 3-4 it only shows as CDC.FromPage = 3
Any ideas