Validation not working for Lookup field

[Mohamed_Fazal1]

Hello.

I created and app for stock counting. I have one table of all the products. And another table to add the counted products. Users keep adding products that they count, so any given item may be repeated i.e. as it may counted in two different locations.

The counting form input users can enter barcode, or item code or item name, once either of this is entered the lookup fields get search the product table to find the mathing product and reads the internal reference ID of that product. 

The problem i have is if any user simply add a product name or item code that is not found in the product table, the form is still accepting the entry and saving the inputs. I want to block this scenario to save only if the lookup fields successfuly finds a valid product from the product list.

Please help. Thank you

Fazal