You could try writing a C-program, but depending on the construction of the Bizflow application, this may give false results. You could try a shell script, but again - it may give false results.
Without knowing the architecture of the application (language written in, original platform, etc...), it will be quite difficult to generate something yourself; you need to mimic exactly how the program allocates memory, handles disk I/O, stores user spaces ... ... ... and on and on.
Unfortunately, there is no simple canned solution for something like this. You can look at TPCC numbers, but I don't put alot of value in them.
Contact your vendor and see if they have a load tester or a "hardware compatability listing". With SAP, they have a worksheet that you can fill out with the needs you have (# of users, expected response times, etc) and the hardware platform you intend to use - and they run it through a magic program and come up with a hardware recommendation.
Every application is different, so to come up with a benchmark application - this would be quite difficult.
Good luck, Bill.