How to generate a random number with $EST

Dear NONMEM Users, I'm developing a model with NONMEM6|7. In this model, I need to generate a random number at every time step. The problem is that the use of the function "CALL RANDOM (2,R)" is supposed to be only for simulation, isn't it? Thus, is it possible to generate a random number at every time step with NONMEM? Does anybody know how? This is part of the code that does not work (it's not working because the condition ICALL.EQ.4 never happens and for that it's not getting into the "if", but on the other hand, in order to use the function RANDOM(2,R), such function requires ICALL.EQ.4): ... $SUBS ADVAN6 TOL=5 $MODEL ... $PK ... IF (ICALL.EQ.4) THEN CALL RANDOM (2,R) ;Rand number in[0,1[ T=1-R ... ENDIF $DES ... $ERROR ... $ESTIMATION MAXEVAL=0 NUMERICAL METHOD=COND LAPLACE LIKE CENTERING PRINT=2 MSFO=msfo3 Thank you! Nieves -- -------------------------------- Nieves Velez de Mendizabal, Ph.D Departamento de Farmacia y Tecnología Farmacéutica Facultad de Farmacia Universidad de Navarra Phone: (+34) 658 732 851 Phone: (+34) 948 255 400 ext. 5827 [email protected]