Chris,

Try

SELECT OrderID FROM Orders ;
  WHERE (vp_ItemID < 0 AND  Orders.OrderID NOT IN ;
           (SELECT OrderID FROM LineItems ;
               WHERE LineItems.ItemID = ABS(?vp_ItemID)))  ;
	OR ;
  	(vp_ItemID >= 0 AND Orders.OrderID IN ;
           (SELECT OrderID FROM LineItems ;
    	     WHERE LineItems.ItemID = ?vp_ItemID))  

>I have a query where the view parameter is used to generate a subquery:
>
>

>SELECT OrderID FROM Orders ;
> WHERE Orders.OrderID IN ;
> (SELECT OrderID FROM LineItems ;
>  WHERE LineItems.ItemID = ?vp_ItemID)
>

>
>This works just fine, but I want to be able to supply whether vp_ItemID is IN/NOT IN the subquery. After multiple attempts, many of them causing C5s, I'm here looking for a way to accomplish this.
>
>
>The following code in the View Designer causes a C5 on VFP8 SP1/Win2K SP4.
>

>SELECT OrderID FROM Orders ;
>  WHERE IIF(vp_ItemID < 0, ;
>  Orders.OrderID NOT IN ;
>    (SELECT OrderID FROM LineItems ;
>     WHERE LineItems.ItemID = ABS(?vp_ItemID)), ;
>  Orders.OrderID IN ;
>    (SELECT OrderID FROM LineItems ;
>     WHERE LineItems.ItemID = ?vp_ItemID) )
>