Easier IOV modeling

Hi The Introduction to NONMEM 7.x documents include a section entitled "Easier Inter-occasion variability modeling" which describes a quicker way to code IOV. $ABBR REPLACE ETA(OCC_CL)=ETA(4,7,10) ;when OCC=1, eta(4) to be used: when OCC=2, eta(7) to be used, etc. ... $PK CL=TVCL*EXP(ETA(1)+ETA(OCC_CL)) When this approach is used, OCC must be a data item defined in $INPUT. Is there a similar way to code ETAs using a dynamic variable defined in $PK? Thanks Sebastien