thank you for your quick reply.  Unfortunately I thought that would be the answer.  As a software developer/designer for 35 years who has worked on numerous applications I can honestly say I've never designed a filter system that did not allow both AND and OR conditions.  Of course, it can present some confusion for novice users since you might have to introduce the concept of parenthesis [ (A and B) or C vs. A and (B or C)]  but for advanced users it would be valuable.