Calculating the sum of a combo box?

[Luke.F.14]

Hi

I'm creating a database for my a level IT course about car hire. On my Order form i have a sub form containing details about each car that the customer has hired aswell as the date in and out and a combo box containing the total price (calculated by multiplying the price per day of that car by the number of days it's hired for). I would like to be able to create a combo box on the main order form that calculates the overal order total price - which would be the sum of the total price boxes on each car in the sub form. Since it's only one field that's repeated for each car that's hired by that customer i can't do the sum of them all - it's only one field. Does anyone have any ideas?

[aytee111]

A combobox is an object that provides the users with multiple entries whereby they make a selection. This should be a textbox, not enabled.

On the footer of your subform add a textbox with a control source of : =Sum(price/day * numdays). This will give you the order total. You can additionally add a textbox to the main form altho there is no need.

[Luke.F.14]

Yes i meant text box not combo box, sorry. I just tried this however i just get #error appear in the text box. This is what i entered as the control source:

=Sum(([Date In]-[Date Out] +1)*([Car Copy ID].[Column](8)))

([Date In]-[Date Out] +1) is the number of days and ([Car Copy ID].[Column](8)) is the price per day.

[aytee111]

Make them fields on the subform which you can then sum. Do the calculations in the record source for the subform so that they have actual field names.