You can provide input options just like you would do on the command line when launching FastCap from the shell.
To be clear, here you are just passing a string with the input file name.
couldRun = FastCap2.Run("""" + path + "sphere"+CStr(i)+".qui""")
You can pass more complex strings, like:
that launch the simulation on the list file mylistfile.lst with a tolerance of 2%.