Thanks FishVal.
Really appreciated.
I have managed to do it using VB code.
But, I'm still amateur. So, if there is any problem again, I'd like to ask all the experts here including FishVal.

Cheers.

Hi All,

I created a form to show current stock of specific tool part no from one query. The current stock of a specific tool part no = All Purchased Tools - (Tools in Repair if any + Scraped Tools if any). Specific tool part no is chosen from the unbound combo box.
The problem is when a tool has never been repaired, the form goes error. the form can only works when a tool has been repaired. in another words, the form only works...