Hi There
Yes this is possible.
What you need to do it provide a peer IP address on the 837.
On the VPN3000, you would create a group with peer address as 0.0.0.0.
So this kind of acts as a dynamic crypto map.
make sure the key matches correctly.
This link I am sure will help you configure the VPN3000.
http://www.cisco.com/en/US/partner/products/hw/vpndevc/ps2284/products_configuration_example09186a00801dd672.shtml
Do let me know if you run into some issues.
Thanks and Regards
Wakif