[AccessD] Padding text values

I thought I could pad a text value with a simple expression in Format or
Default, but can't come up with it -- I know I could write a function to do
this, but seems this should be a simple property expression. I don't want to
force the user to enter 045 instead of 45 -- I want to add the leading zero.
I'm pulling a complete blank. 
 
Susan H.