Summing two list boxes on a form

[TinaCa]

on the AfterUpdate event of a combo box i do a refresh which updates the two listboxes on my form with a single value (a sum from the queries used as their individual recordsources). I need to add those two values together.

I found in another post that access sees list box values as strings so I have set variable to convert the strings to currency.

However, when the list boxes get their values (after the refresh) the text box is not updating with sum.

lstbox1.recordsource = ELECT Sum(([ExtraCost]*[ExtrasQty])) AS ExtraTotal FROM CompanyInformation LEFT JOIN tblCompanyExtras ON CompanyInformation.CompanyAccountNo = tblCompanyExtras.CompanyId WHERE (((tblCompanyExtras.DateBilled) Is Null) And ((CompanyInformation.CompanyBillingDate)=Forms!frm CreateInvoices!cboPrntInv));

Lstbox2.recordsource = SELECT Sum(CompanyInformation.CompanyContractAmt) AS SumOfCompanyContractAmt FROM CompanyInformation WHERE (((CompanyInformation.CompanyBillingDate)=[Forms]![frmCreateInvoices]![cboPrntInv]));



I was using
Dim MAmt as currency
dim Eamt as currency

MAmt = me.lstbox1
EAmt = me.lstbox2


I need the textbox to =(sum MAmt + EAmt).


It is not updating after the refresh On what event do I need to put the sum function or is there another way entirely?
OK part of the problem solved - I need to use me.lstbox1.itemdata.

Next issue the listboxes store the data as a string. I have tried CInt(lstbox1.itemdata) to set my variable value but I am getting an overflow errror.

Now on what event to put it?

[TinaCa]

OK here is the solution.

First I needed to select the correct data in the box i.e. me.LstBox.ItemData(0).

Then I needed to convert it to a currency so the calculation for the text box looks like this.

me.txtTotal = CCur(me.lstBox1.Itemdata(0)) + CCur(me.lstBox2.ItemData(0))

Hope this helps some others I've been fighting with this for several days.