Parameters
If you specify a parameter in a query, can an expression in the query refer to the value that was entered? Please advise.

Yep. Refer to it the way you would refer to any other column on the query builder. So, if column 2 reads "Expr1:[AskMe]" which generates an "Enter Parameter" dialogue, column 3 can read Expr2: [Expr1] * 2 and will evaluate to <whatever you entered> * 2.

As far as I know, though, you only get to enter such parameters once, when the query is opened, so Expr1: in the above example will be whatever you answer for every record in the query, and so will Expr2. If you want a different value for each record, you'll need to get it through a control.

--Expressive Mac