group problem

[Guest_imported]

I have table of categories with cat_id as primary key then I link to item table where each category has different items linked by cat_id and unique item_id .so I create a group of category id then summarize item ids and then I want to group all these two groups on the basis of user_id which is also a common field between all these three tables . so how do I do that. When I try to create a group with user_id as sort parameter it gives me an error microsoft access error .. so please help me!!!!

thanks,

 

[emallon]

How do want the report to group?

By Cat_ID
By Item_ID
By User_ID

Is this correct?