Is this what you are thinking of doing?
Set temporary values for each of the 9 option sets to the value selected (if not null).
Then count the temporary values that are not null.
If count = 2 then concatenate the temporary values held (or sum if they are numerical values) for the non-null values.
yes in the option set i have two values 0 or 5 and when the user choose an option i would like it to update another field on the form with the sum