I want a text box to contain data which is a calculation based on 2 other control field values - only if it's value is null (ie the current value of the column in the database is null).

So I entered =([control1]\*[Control2])/1000 in the expression builder for the default value property - however the result always shows the textbox to be empty (even tho control2 and control2 contain values).

How can I achieve this? Can such an operation only be done in code-behind ie VB??

thanks,

KS