workflow rule not working

Hey Folks,

I have created a rule which returns users when i input a cost center and release code . for example for cost center 11000 and rel code C1 it returns me 5 users. The rule works fine in simulation but when the requisition is created it goes only to the first user only. The remaining users are not getting that work item. I have specified the rule in the expression . Did i miss something while customizing the workflow. Please let me know what I m doing wrong.

Thanks in advance.

Rock