[rules-users] Setting value in LHS for access in RHS

Hi folks, I'm trying to set up rules where the RHS is able to refer to a value set in the LHS so that it can perform its logics slightly differently. I'm able to use $var to pick out fields from facts in working memory. However as far as I can tell I'm not able to set a new value. I'm setting up a DSL to drive guided rules in guvnor and in the RHS I need to know which value was picked from a drop down list in the LHS. Cheers Steve