Crystal Formula - SQL

I started with this selection criteria:

({@.Meditech Date to PC Date} in {?Beginning Date} to {?Ending Date})

Then I did this:

{@.Meditech Date to PC Date} in {?Beginning Date} to {?Ending Date} and
({LabSpecLPatientIndex.Prefixes} in ["IM", "R"] and {LabLSpecResultTests.Result} <> "")

I got data just fine on that.

Then I further altered it with this:

({@.Meditech Date to PC Date} in {?Beginning Date} to {?Ending Date}) and
(({LabSpecLPatientIndex.Prefixes} ="IM" and {LabLSpecResultTests.Test} = "902.9550"
and {LabLSpecResultTests.Result} <> "") or ({LabSpecLPatientIndex.Prefixes} ="R" and
{LabLSpecResultTests.Result} <> ""))

And I get no data. What did I miss? I want all records with between those dates, that have prefixes = IM or R that have results (not null results). If the prefix = IM, then I only want it if Test = "902.9550" ...but I want all records with a Prefix R.

TIA.
Briana{@.Meditech Date to PC Date} in {?Beginning Date} to {?Ending Date} and
({LabSpecLPatientIndex.Prefixes} in ["IM", "R"] and {LabLSpecResultTests.Result} <> "") and {LabLSpecResultTests.Test} = "902.9550"