I have 5 tables in which all documents get stored. Further calculation fields could only be done in queries. Tables do not allow that calculations. In a new query where I need to have an expression to calculate the customer balance. I need an expression to work. I trained myself now for 120 days, videos etc. Other ecpressions work but I battle here. All sales invoices are in q06InvSal query with subtable and query q06InvSalSub. My expression in a new query is DSum("[issexclVat]","q06InvSalSub","[CmbEntID]=" & [CusID] it does not return anything. In my new query the field CusID is pulled down. CusId is a foreign key to CmbEntID and I dont see why it dont work Is there another expression that could be better?

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Reply from Alex Hedley:

You could use an Aggregate Query. These are covered Expert 11.