Melissa, the calc you describe is probably this:
IF [customer type]=1 THEN 'credit' ELSE 'debit' END
But I suspect it might be more complicated than that. You say 'filter on a dimension based on the filtering of another dimension'. In your calc where is the 'other dimension'?
Transaction Type is the other dimension.
OK, I see. The boolean error you are getting is because you can't put booleans after the THEN. They all have to go in front (left side) of the THEN. So you're calc would be some variation of this:
IF [customer type]=1
AND [Transaction Type]='Credit'
THEN [Transaction Type]
ELSE 'debit' END
Both booleans are before the THEN.