[murx]

I have a very similar problem:

I want to iteratively change the velocity of a wall (U). Here is a simplified version of my CEL:

U = areaAve(U)@WALL + delta-U
delta-U = force_x@body / (mass*delta-t) * relaxation-factor
This version generally works, but the problem ist that the function areaAve(U) uses the conservative values. So U does not converge to the right value.

So what I tried next ist basically what stumpy and Glenn suggested. I created an additional variable (Uvariable), used the option algebraic equation for Uvariable and entered U for the equation. Then i simply used:
U = Uvariable + delta-U
When I do so, I get the same error as siardica:
Error processing expression 'global frame vector associated with Wall U'.
The expression is invalid because:
uvariable is not available for use in this term

How can I fix this? Is there maybe I way to make the solver use the hybrid values for areaAve(U), so I can use the first version?