Hello DrAmine,nfirst step I do, is to set the Number of User-Defined Memory Locations to 1.nAfter that, the compiling of the UDF occurs.nThe messages I get from the UDF say that C_UDMI(c,t,0) = 1,nbut fot the second source term the cells of C_UDMI2(c,t,0)=0. So the Values of C_UDMI(c,t,0) doesn´t get transfered to the second DEFINE_SOURCE macro.nWith best regards nisaps1860nn