Expanding tables with calculating form fields?

[macropod]

Sure. If the displayed output is 001, 002, etc., and you want to multiply that by something, you could use a field code like:
{={REF Dropdown1}*5 \# 0}
Unless your dropdown only ever displays numbers, though, you might want something like:
{IF{REF Dropdown1}<> "Select an item" {={REF Dropdown1}*5 \# 0}}
where 'Select an item' is the default text' or, if some of the selections might not be numeric:
{IF{REF Dropdown1}={=0+{REF Dropdown1} \# 0} {={REF Dropdown1}*5 \# 0}}