As title, I use in the web url protocol calling a winform procedure, in the Process of acquiring polling Process at the top in the procedure handle, program after the operation of the Process to obtain the access denied error, how to deal with this?

Restrict user access Process is mainly want to leave form (anti-cheating), the main idea is through the top constantly polling in the Process of the handle to the current window handle, ranging from the mandatory current form on the top floor,
Whether there's a better way to restrict users leave form (I once through constant setting topMost device in time, this can really achieve the effect, but the form you need to call external programs, when an external program to run after the page will be the current window shade,)?