LOOKUPVALUE should work fine here. The problem is your use of VALUES, which returns all of the unique values in the specified column. For LOOKUPVALUE to work properly the third term needs to be a unique scalar value. Thus if DefaulRate is a calculated column, you can just strike VALUES and it should work because you have row context within the calculated column. If it is a measure, you will need to replace VALUES with SELECTEDVALUE to return a single value.