time step size in Custom Field Function

Tong

Dear all:

When I difine a custom field function, I want to use the current time step size (my case is unsteady) in this function. But time step size is not in the operand list. Does anyone know how to solve this problem?

Actually, I have a UDS and I want to record the quantity of the UDS transported throught a corss section which is not a boundary at every time step. I know how to achieve this if the corss section is a boundary (by using UDF), while in case it is not a boundary, I define the corss section by iso-surface first, and then the custom field function I mentioned above. If this is not a feasible way, can you give me some suggestions?

Thanks a lot.

Tong