You will have to ask yourself how you are going to differentiate between Quantity and Unit Price. Technically they are both numbers. How do you determine if the Unit Price was entered into the Quantity field?

Whatever rules you decide on I would use the Before Update event.

Thanks for the quick reply Kevin.  I understand that both fields are numeric values.  My question was more along the lines of the Ext Price remaining at 0.  I can see a novice user making the mistake of leaving one field as 0 (qty or price), thinking they had entered a value in both, then moving on and not noticing that the Extended Price was zero.  Also, when you suggest a Before Update event, would that be for the subform?  Thanks.

Hi Leticia, it may depend more on your "business rules" whether to alert the user about the zero price or not.  There may be good business reasons for charging zero price, such as bonus giveaway items and the likes.  My old job involved order entry too.  When we entered an item into the order, the "standard" price was immediately looked up from the product's record and put into the order.  The user could then change or keep the price.  So there would be no "mistake" per se, and nothing to alert the user about -- unless the product table had the wrong standard price.  Only one person was allowed to access the product table.  So if the price was wrong, we would know who to blame.  This is just an example, but it demonstrates that this involves business rules that differ from company to company.

That's a good point Kevin.  In that case zero price would be acceptable. And, I can see where IF your business rule stated "No zero price allowed" (and a "standard" price was auto-generated), you could handle that situation with an item discount (e.g. 100% to produce the negative price for the sale).  Thank you!