@skylinekiller
I don't think you can?
Well, I think there could be a way, but you don't need a router for that, at least with Windows.
Don't need that either if you phone has 'hot spot' capability? That said, when I go places where I have to wait, I take my iPhone and iPad with me. If they don't have wireless available I turn on the iPhone's Hotspot and connect the iPad to it. All I can say, compared to normal wireless anywhere, it is painfully slow. It is a 5G connected phone no less by my carrier, T-Mobile it seems doesn't give it full speed via a Hotspot. I wouldn't imagine it would work feeding a router to many devices with it would be much better?
Router's all require a WAN connection from your ISP, via a device that handles the input and outputs WAN to be used. I don't know of anything that does that via a wireless connection to a phone or Cell Carrier (other than the ones they sell, like T-Mobile).
Most carriers probably also sell Mobile Hotspots, and they are basically a router. I do think you can feed that into a router, but it would only duplicate the Hotspot function in most cases?
I may be wrong about feeding the router the signal from a phone, others might know better than mee? See if you get a different answer? I'd be interested too if/when the ISP signal is lost.