Ok, here's what you'll do:
1. Create a SQL Expression. I'll call this {%Filter}.
CONVERT(UNIQUEIDENTIFIER, RIGHT(CONVERT(VARCHAR(MAX), 'Table'.'Field'), 36))
Select the field that you want to use from the list in the editor instead of just typing it - that way you'll get the correct format on it. This is SQL syntax instead of Crystal or Basic syntax.
2. In the Select expert, select the field that you want to compare, "is equal to". Then edit the formula. Initially formula will look something like:
{field} = ""
change it to
{field} = {%Filter}
-Dell