How to test for null values using the dreamweaver datasets

Hi,

I am using a dreamweaver dataset that has a query for totalling values in a database in a VB ASP.NET page. The code to display my total is (as placed by DWMX when you drag the field) :

<%# QryBasketTotal.FieldValue("TOTALAMOUNT", Container) %>

This displays the totals fine, but not formatted to 2 decimal places so I tried the following:

<%# formatCurrency(QryBasketTotal.FieldValue("TOTALAMOUNT", Container),2) %>

Which also works UNTIL the value of "TOTALAMOUNT" is empty or null, then it falls over in a big heap.

So, my question is, how can you test for a null value in ASP.NET on a dataset?

I have tried making my own functions to do a simple if <blah> is NULL then... but it would appear NULL is not supported, so I tried dbNull.Value (as found on the web):

function DisplayTotal() as String

      Dim Container
      if QryBasketItems.FieldValue("TOTALAMOUNT", Container) is dbNull.Value  then
            DisplayTotal="0.00"
      Else
            DisplayTotal =formatCurrency(QryBasketTotal.FieldValue("TOTALAMOUNT", Container),2)
      End If
End function

But THIS fails with "System.FormatException: Input string was not in a correct format."

PLEASE PLEASE PLEASE, does anyone know what I am doing wrong?

Thanks

Jimbo