I’ve never done it, but it sounds like Ad-Hoc in reverse…..which is what ICS (Internet Connection Sharing) is for.
For ICS to work in this case, you will need 2 NIC cards in your PC or Laptop.
I’m assuming that’s what you have? You say you have a Wireless NIC plugged in for access to your Cellular Provider…..so do you also have a built-in NIC with an RJ48 plug that you would typically plug into a router or modem?
If so, you can use the wireless card to get internet to the PC/Laptop, then you set up the wired NIC for ICS which will make it something of an access point. You then plug a wireless router into that port, and it will share it wirelessly.
So the extra PC NIC becomes something of a modem or access point for the router, and then the router becomes a wireless supplier to the iPad.
In theory, that could work. Some problems though.
1. You have to have a second and free NIC in your PC/Laptop.
2. It sounds as if your PCs are all Laptops. For ICS to work, you’d have to hardwire a wireless router to the laptop meaning it’s no longer portable.
3. If the router and your wi-fi provider are on the same channel, it could cause problems (collisions, dropped connections, etc).
Without a wired internet connection, this is a tricky situation.
Another way that might work, but that would require two routers, is to have one router set up as a bridge to get the wi-fi signal from your cellular provider. Then hardwire a second router to that so that it provides wi-fi to the iPad. That is cludgy as hell, and I’ve no idea if it would work. I mean, if the iPad can’t access the wi-fi from your provider, I doubt an off the shelf router could.
Have you tried to get the iPad to see your cellular provider’s signal? The iPad should be wi-fi enabled (built in, no external plug in hardware needed), and should be capable of picking up the signal from any hotspot…..unless your provider is intentionally blocking it?
Your best bet would be to call your cellular provider and ask them how to get your iPad on their network. I’d imagine they have faced this before and will have an answer. Who is your provider?