Re: Conditional Sum ( equal for 1 column, and ignore another column )
then what you need to do is a conditional dimension using if() that will evaluate the condition and display the dimenion value or NULL. Then enable checkbox 'show nulls' on the dimension to hide the rows that don't meet your condition.
ex: if ( <condition>, dimensionfield)
If you use a measure expression with set analysis that is fine, but you will have to wrap in aggr() function for it to evaluate at the right dimensional grain.