Question : Query questions

I ahve a query that using an expression to calculate.

Revised Bill
RevisedBill: Sum(nz([tblrevcodebill.originalbill])-nz([tblrevcodebill.feereduction])-nz([tblrevcodebill.additionalreduction])-nz([tblSettlem.Settlementamount]))

This works fine.   Now what I need to calculate is:

TotalSavings:  which would be Originalbill - Revised Bill

Everytime I try I keep getting errors.

The syntax I have tried is :  
TotalSavings:  [OriginalBill]-[RevisedBill]

Any help?

Answer : Query questions

your Totalsavings can be computed by adding the three deductions

Totalsavings:Sum(nz([tblrevcodebill.feereduction])+nz([tblrevcodebill.additionalreduction])+nz([tblSettlem.Settlementamount]))