Data Extact Widget - How to set maz area size for user

Hi there

Just wondering if anyone can suggest how I can set a limit on area (sq Km's) on the users defined area of interest. So that if they to try to extract an area that is too big (over limit set) they get an error message back.

We have tried doing this is python and in the Data Extact model and this works well in ArcMap. Then when you publish it it doesnt work. So I am assuming something will need to be set in Flex

Thanks

Louise