getting #Error on Continuous form?

[RitaMoloney]

Hi,

I have two calculated controls on my continuous form.

TotalCostofParts
In the control source I have the following;
=DLookUp("[TotalCosts]","qryStoreJobs","[StoreID]=" & ([tblPartsUsed_StoreID]))

costofpartused
In the control source I have the following;
=[TotalCostofParts]/[UnitsInStock]*[NumberUsed]

These work fine except on the last line where you have a new record, I get a error " #Error " in the calculated fields.

Does anyone have any idea how to get around this problem. I have attached a picture of my form.

Thanks in advance,

 

[RitaMoloney]

Has anyone any idea?