You can apply other pressures at home, cut the phone bill, internet, etc... If you can limit her extracurricular activities with wtihholding financial support for them (kill your internet service and phone service, etc) that may help too.
We don't have full details of household management there, so its a tough call.
If you are in IT you can manage your router to restrict internet activity to a specific mac address (just your PC) for example, as well... so you can lock her out of the internet.
If you pay her phone bill, cancel the phone service and just use your cell phone, etc
You just withdraw any financial support from her that she is using to the detriment of the marriage. If she complains you just tell her that outright - I refuse to financially support your infidelitiy that is detrimental to us and our children - I am not going to HELP you CHEAT - ANYMORE.
Whatever you can restrict her from that can keep her from OM and that is within teh bounds of the law - do it.
