sum first before calculation

[luzz]

The dsum would go on the form. The link I posted demonstrates how to implement criteria with it.

I faced this error when i do dsum. The color "Deep Black" do exist in the system

 

[Minty]

You have formatted that as a field because of the square brackets around it.
I don't understand why you would hard code that color value, but if that's what you were trying to do then you would have to write it like;

DSum("[Our Qty]", "UnmatchNewFabricPOQry","[Color] = 'Deep Black'")

Note that Color is a reserved word, so needs the square brackets around it to avoid other errors .
You really should remove spaces from field names as well they cause heaps of extra typing and are a constant source of errors.

 

[plog]

Weird. You quoted my response, yet you still used the DSum in a query.

As for the syntax error, Minty covered that.