When you call call_external like call_external(p1,p2,p3,p4) what do the four parameters mean?

I have a program that may call Compiler:-Compile to speed up the calculations, but after the program terminates the DLL that was generated still exists on disk. Every time I call on the program, I create a new DLL without deleting it. If I keep calling my program, the disk will get full of temporary DLL's until the disk gets full. I know how to delete using FileTools:-Remove, but I get the "permission denied" error message. I assume that it is because Maple 10 is still using the DLL, so how do I get Maple to free the DLL so that I can delete it?