[rules-users] Rule in decision table

I am trying to write a condition for a decision table and can't seem to figure out how to do it. I have a global variable called area. This is in sq. ft. I have a fact called Item which has an attribute called weight. This is in grams / sq. ft. The Item comes from the attribute called value from a fact named Choice where the sku attribute matches what is in the rule I want to compare the (weight * area) to the parameter for the row. The parameter is being passed in as lbs. Here is what I tried for my three condition columns: CONDITION CONDITION CONDITION mm : Choice sku exists(Item(weight * area > ($param * 453.5924)) from mm.value) exists(Item(weight * area <= ($param * 453.5924)) from mm.value) This did not work. This will work if I remove the formula and just do something like exists(Item(weight > $param) from mm.value). So the syntax is correct except for the comparison that I want to do. Any ideas on how to do this? Thanks.