I am trying to build a GetScalar function that sums a field in a table. My problem is that the IPredicate parameter in the GetScalar function would only accept ONE predicate while I want to send a complete PredicateExpression that is compound of several predicates.

Is there a way to do this ??

IPredicateExpression derives from IPredicate. So you can pass in a single predicate, created by PredicateFactory for example, but you can also pass in a predicateexpression, for example bucket.PredicateExpression