How do I set the parameter of the SQLDatasource in a user control

I have a usercontrol with an sqldatasource control that needs a parameter set.
I put the usercontrol in several pages but the parameter has different values depeniding on the page it is in.
I cannot see the SQLDatasoucre selecting event of the usercontrol in the code behind of the pages so how do I set the parameter of the SQL?
 
Thanks
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