Lookup Formula

I need this to be done in SSRS. In SSRS, I have one dataset that feeds into two matrix/tables.

Field1 Field2 Field3
1 A
1 B
1 C
1 D
1 E
1 F

TableA displays Field1 and Field2.

TableB displays Field1 and Field3.

Only make TableB visible if TableA has letter "B" in it.

I have tried LookUp, LookUpSet, MultiLookUp, CountDistinct, and a bunch of other aggregated functions. CountDistinct seems to work because it returns back 3 counts.

By now you should know how to provide sample dml and ddl for us to work with and desired result as ddl and dml as well.
Please provide these