InfoPath Dev

Thanks very much Matt... Greg's cascading works perfect... However, I cannot get the same thing working for a text box... In the filter of textbox filter refused to accept current()/my:XXX as a valid formula...  Any solutions for this?

I've got a repeating table with several repeating fields, 2 of them are dropdown lists and another one is a textbox. dropdown list 1 is filled by a web service. Whate I want to achieve is: When dropdown list 1 selection has been changed, call another web service (take the value of dropdown list 1 as parameter) to fill dropdown list ...