A function (vba) that sums a table's field and puts it in text box in form

[JuniorWoodchuck24]

Is there a way to define a function in VBA that sums a table's field and automatically puts it in a text box?

Currently I'm using the following:
List Box with it's RowSource the following:
SELECT Sum([Total Cost]) AS Total FROM OverallWeight;

The error I get with this is that it's not really a number value so if I compare it to something else it gives me an error.

 

[DCrake]

You need the DSum("Field","Table","Criteria=Condition") method

David