VBA Code for Textbox: First 3 characters Alphabets next 3 characters numeric

Hello,

I just started writing vba for userforms for excel. I am stuck on this one however...and would like to know what the code would be?

I would like the following to be always true for my textbox

- first 3 characters are alphabets, next 3 characters are numeric, next 1 character is Alphabet, last 3 characters are numeric
-10 total characters.

so something like this : SCN000A000

error message if not match the pattern and if not 10 total characters

Any help would be appreciated.