Questions can optionally be populated from a web service.. Furthermore, answers may dynamically change in child questions, based on the answer chosen previously. It will be necessary to specify which parent question will trigger a reload of the child question. 

Assume the following:

• Question26 list is populated from a web service call WS1. This is the source question.
• Question27 is populated from a web service call WS2.  This question takes the answer to Question26 as an input parameter, can can be considered the target question.

Question27 receives its input from question26 by using a question variable.  Namely "##QuestionID:26##.  

To achieve above configuration, You would need to specify the "Reload answers for questions" setting under web site->catalog behavior. The value should be "26~27". This indicates that the when the source question of 26 changes, then the target question 27 should reload.. This should cause the variable to be resolved. As screenshot shown below.

In the event that you have more than a single pair of questions it will be necessary to separate each question pair with a pipe character ( | )