Eliminate data entry key strokes and mistakes in a cell - Input mask? Textlike?

I want to make data entry in a cell easier so the input person does not have to enter the two constants every single time.

For instance, in column A1 the only entries will be a 9 characters length; ####AA###.

The AA never changes and the other charters are numeric, fixed length 9 character total.

Some commands researched are textlike and input mask. Input mask sounds best but in any case don't know how to use them.

Would guess the textlike formula would be like this - but how to actually use it no idea
"=TextLike(A1, "[0-9][0-9][0-9][0-9][A][A][0-9][0-9][0-9]")"

I search our forum but no hits on textlike, although an input mask might be better.

Thanks