Calling the same userform, continues to run through after the "call"

Alright here's my issue:
I have a user form that allows the user to enter an ID #. I have code that checks to make sure the ID# was entered correctly. If it wasn't it prompts them to check for typos and reenter. Then I do userform.show. Effectively starting over. But the problem is that it calls the userform, runs it with the "fixed" entry, completes the user form code, then continues from the previous point where the error was found. For example,

User enters ABCDFG
code checks to see if there is a mistake, there is, it should be ABCDEFG.
MsgBox("typo, please fix")
userform1.show

User enters ABCDEFG
code checks to see if there is a mistake, there isn't
code runs all the way through

code continues from check #1 with ID# = to ABCDFG

I don't want it to come back to where I called the next userform and continue. Is there a way to do what I'm trying to but only have it run once. Is it clear what I'm asking?