My brain is smoking! 
First of all, thanks Kem - that now works, except that I have to check for a single “0” and then change it to “00”, in order for the code to be valid Hexadecimal.
Tim, is there any advantage using your way instead of Kem’s??
Syed, thank you for finding the repetitive loop in the beginning.
I outlined my method because I was not aware of Widow.Focus. Since that does most of what I recommended, you can skip everything except the change to TextChange.
So basically, remove the GotFocus and LostFocus events completely; Delete the property; And modify the TextChange event (to that as Tim advised).
GOT IT !
Right. Except you give credit to me instead of Tim because well, you just do!