>A VFP_based application is used on LAN.
>InstallShield setup creates on workstation's desktop shortcut and program menu shortcut to the main application that is on server.
>During WorkStation installation the path to program("target") and to "Start in" folder are not known.
>InstallShield creates 2 environment variables my_prog and my_startdir. I can read their value by using VFP function GETENV().
>I would like to use them for substitution in shortcut fields Target and Start_In by placing %my_prog% and %my_startdir% in corresponding fields. Since sometimes LAN configuration changes, a procedure to locate server program and start_in directory is used.

That's a job for InstallShield to setup the starting folder and default folder.
We usually check if the data is there where it is supposed to be. If it is not we run a GETDIR() dialog so the user could choose where the data is located and write his/her choice in and INI file (hate to write in registry).