Combo Box with Input mask

I have a combo box with a record source that looks up the data wanted. I have
added a Input mask to the properties so that the user doesn't have to enter
the "-" when entering the number they type in the combo box. Prior to adding
the Input Mask, the user could start entering data and the combo box would
auto fill the number they entered as they go. Now with the input mask it
automatically enter the first number found based on the first digit entered
and moves the cursor to the end of the feild which requires them to back
space to the second digit to then start entering the rest of the number. Is
there a way to allow the user to enter the number without having to back
space?