Thank you!

Great! Thank you both for your help

Thank you... that worked. The decimal number is 4 digit after the calculation; What is the easiest way to change it to 2 digit?

Thanks but I'm still the same error message. I think the issue is +'GB or +'MB'; when I remove this it runs fine.

Thanks guys, I don't think it will work the way I wanted it to work for the exact reason stated. Please disregard.