I think what you're looking for is the WorkingDir property in the Icons section entry. For example (from the Inno Setup Help file):

[Icons]
Name: "{group}\My Program"; Filename: "{app}\MYPROG.EXE"; WorkingDir: "{app}"

>How does one get INNO to create an icon with the default directory being in the start field for the icon.
>
>

>Target      c:\test\myprog.exe
>Start In    c\test
>

>
>I can get the target correct but nothing shows up in the Start In field.
>
>It been probably 5 years since I last used INNO and didn't seem to have a problem then. Must be ole age creeping up on me and the fact I overwrote all my old INNO stuff doesn't help.
>
>
>Thanks in Advance
>Gaylen