About porous jump B.C.

Susan

I want to automatically adjust the pressure-jump coefficient in the porous jump panel (B.C.). The adjust basis is the x-velocity. For example, in one porous plane, we divided it to several square, after each 200 iteration, the UDF can check the x-velocity value on each square automatically, and to compare the value with the criteria value, if the relative difference between the actual value and criteria value is 20%, we'll adjust the pressure-jump coefficient in this range. How can I do it? which place I can input the UDF? or any suggestion to get the same purpose?

Thanks!