still a little new myself but here it goes..someone else comment if I miss a
step..I'm not sure if you are you looking at it in table format or if you
have a form already.

If you are looking at it in table form then you could create a second table
with two columns, the code and the dollar value. you then need to create a
relationship between the two connecting the two code fields. You should click
both the enforce referential integrity box and the cascade update box. That
tells access to update your form when you update the dollar value in your
second table.
          You could then use the form wizard to create a form, selecting
both the information on the main table you need and the dollar value from the
other table. It should create a form with all the controls you are looking
for.