Number keys on a userform

I have a large userform (the size of the entire screen) that I have added some buttons for numbers. I would like to have a macro that will input the number in the active cell. I have the macro to put the single digits in using the activecell, insert formula "7". But I need to input mulitple numbers in the active cell. Like 34, by hitting a 3 button and a 4 button. How do I do this, if you can give me a starting point to at least start researching from.

Thanks a Million!!