Run SQL Scripts: Define variables whose values are prompted

I am aware that one can use ? in a script to be prompted. I have a script
from an SQLRPGLE program that I am trying to test in ACS Run SQL Scripts;
it uses a few variables several times. I would like to be prompted once
for each variable. For example:

select * from testfile a
where a.DistrictA = :inDistrict or a.DistrictB = :inDistrict
and a.Region = :inRegion;

The above is a simplified example from the one I am using where :inDistrict
is used seven times in the script. How can I be prompted once for
:inDistrict and once for :inRegion?

I tried SET and DECLARE, but those were just WAGs. Google was not my
friend, but I'm not sure I'm even searching on the right terms.

- Dan