We would like to limit our users from proceeding to a certain stage if no products have been selected on an opportunity. RIght now, it doesn't appear there is a way. But it's important that products be mandated and fear they won't be used if there's no trigger to ensure they're selected. Is there a way around validation rule limitations that only work on object fields?

We would like to limit our users from proceeding to a certain stage if no products have been selected on an opportunity. RIght now, it doesn't appear there is a way. But it's important that products be mandated and fear they won't be used if there's no trigger to ensure they're selected. Is there a way around validation rule limitations that only work on object fields?