In reply to srikanthvvs1:
You can override the behavior of a system task by writing your own VPI implementation of it in C. That’s relatively easy if you want to override all calls to $random, but if only some, then it gets more complicated to know which ones, and you have to implement the normal behavior of $random for the others.
But this “I can’t edit the files” is nonsense. If you can read the file, you can edit a copy and replace it in the compilation process.