Crystal Reports Select Expert (Help with Formula)

Message

   I have a report that I would like to filter through the selelet expert with a couple of different criterias.

The report is basically a reorder report that looks at all purchased inventory items and then groups them by vendor. What I would like to do is further filter this report through the select expert but I think it would require an IF formula or something of sorts.

The reports shows a columb field of {Days to stock Out}, {Available on Hand} and {Usage YTD}

Here's what I'm looking to acomplish.  I don't want the line item data for a part to display in the report if {Usage YTD} is less than 1, unless the demand {Available on Hand} is less then 0. i.e. -1 On Hand

I would appreciate any help in getting this to work!