Add 1 to the last number in a textbox in a userform

I want to add a 1 to the last number in a textbox in a userform. I can add a 1 to the last number if the last number is less then one:

ex. popcans 1
popcans 2
popcans 3

Once the number gets to 19 it adds a 1 to the 9 and the number becomes 110 (1 & (9+1) = 110)

I want the last number to increase by 1 regardless of the number (5, 15, 19, 29, etc.)

Can someone help me?

Thanks Tom! Works Great!