Inclusion of Analytical Expressions in NONMEM control file

Dear NONMEM users Has anyone ever tried to include analytical expressions within a control file in NOMEM? I guess that would obviously imply the use of a routine alternative to the $DES. I'd appreciate if you could provide me with some tips or a short example on that. Many thanks in advance, Georgios Georgios Vlasakakis, BEng Post-Doctoral Fellow GlaxoSmithKline, Middlesex, UB11 1BT, Stockley Park CPMS Development and https://connect.gsk.com/sites/cpms/TandD/Pages/default.aspx Quantitative Sciences, R&D Internal Phone Number: 792 2047 External: +44 (0) 208 990 2047 email: [email protected]