如何在sharepoint顺序工作流中的replicator活动中加载外部数据？

I'm trying to make a really simple sequential workflow on sharepoint. The target of this worflow is doing a repetitive task creation over an item added. My problem is that the number of task tobe generated are stored in a sharepoint list so, before the replicator activity runs I have to check this list and get the number of task to be created sequently. When I do this operation the workflow only creates one task and the workflow status is "finished". However, If I set the number of task with a constant the workflow works fine.I'm trying to make a really simple sequential w