Hey Joe,
The easiest way is to assign ControlSource in Grid.Init (or later on, when you know exactly the value of the control source). Experimenting with UDF in CS usually tends to cause funky errors and weird grid behavior...
However, if you have to have this UDF, post the code...

>I put a function in the ControlSource of one of my columns and now I get a blank grid!
>
>My function is being passed a numeric argument and I read something in the Dec98 FoxAdvisor that said I couldn't do that, so it suggested passing a dummy character argument as well to get around it.
>
>Still no luck...
>
>Any ideas?