Forward calls to cell if no answer extension after x rings

Can someone enlighten me on how to set it up so that if someone
calls my extension, after X amount of rings, it will forward the call to my cell
phone?

or

could i set it up so once it goes to my voicemail, i could tell the user to press 777 to have forward to my cell phone?

any of these scenarios possible? if so can i get a step by step?

Thanks!

yes both are possible and have been covered in the forums and other placed on this site already.

Let’s see ways it can be done (Just to name two):
vmx locater
Ring group

If you look in the documentation section of the site under How To’s or Tips and tricks you’ll find several posting on how to do it.