InfoPath Dev

I have two drop-down fields and need to auto fill value base on another field value in both way. I follow the instruction in http://www.bizsupportonline.net/infopath2003/autofill-fields-infopath-dropdown-selection-secondary-data-source.htm to add rules in both fields. If I just enable one rule, it works correctly. However, if I enable rules in both fields, nothing show up in both field. I guest it runs into a infinity loop situation. Field A's rule changes value in field B, then field B's rule fires back to change field A value...I cannot find an "exit" or "change" condition for rules. Any suggestion of how to fix this problem will be appreciated.

as far as i understand,you cant have rules on  two fields to update each other, they will simply run into infinite recurrssion.

 You can create a rule as the first rule in one of the fields' set of rules that has a condition, and the option "Stop processing rules when this rule finishes."  That should stop the infinite looping, but it's up to you to determine what the stop condition should be.

Thanks for your suggestion. I already try to set the condition to another field must be blank. That will be OK if I only allow users select once.