In reply to JSH:
You should be able to do it but it will be very boring. Endurance training can be boring even when you're moving around on a climbing wall. You also won't get the benefit of developing your movement patterns by being on a climbing wall.
The key to doing it with the equipment you describe is to get the correct load on your arms for your desired goals.
You can adjust the load on your arms by taking some weight with your feet. Keep your feet on the ground. You can use a chair if the ground is too far away. The further away your feet are from your handholds horizontally, the more weight your arms will take. Aim to find a location where you can use the holds you want for the duration you are aiming for. As you progress, either increase the duration, move your feet further away, or reduce the hold size depending on your aims.
When doing each set, keep your hands moving around various holds as if you were climbing. The repeated loading/unloading is an important part of building endurance as it 'teaches' your forearm to deal with pump. Try to simulate how long you may hold on to a hold for when actually climbing.
Good luck with it.
I hope this makes some sense,
Mehmet