I am sooo close. Here is the formula:

[formula]
if {?TradeIDParm} > 0 then
{ado.Trade_id} In {?TradeIDParm}
[/formula]

I changed {ado.Trade_id} = {?TradeIDParm} as you suggested to {ado.Trade_id} In {?TradeIDParm. This seems to work well.

What do I need to change {?TradeIDParm} > 0 to?

If I can get that this whole thing is solved.