newbie requires help

[Douglas Mackay]

Rod the debugger keeps on comming up with :
 . There was an Execution Error at 1:02:50 PM
Error description:  Function: error in function handler
Object: button id 1003 of card id 1002 of stack "C:/Program Files/Revolution 1.1.1/Sample Stacks/Age Calculator.rev/Age Calculator.rev"
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put whichage (firstDate, secondDate) into dateholder
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Value: whichage
error hapens after entering assesment date 

cheers 
Douglas