User modifiable functions

Joel

Reading the install instructions on star-cd it says the to modify the user subroutines i need a copy of absoft fortran compiler. Do i have to use this one or can i use another? I have a copy of Compaq visual fortran staring me in the face and i dont really want to have to get another package unless it is vital. Also hoiw modifiable are these user subroutines, i am looking to modify the viscous terms so i can model a viscoelastic-plastic fluid, do you think that the sub routines are adaptable enough or will i have to get my hands on a source code of another package?