Sure you can. Assuming your only want to monitor two physical ports, just have them both use the same destination port and you’re good to go.
Info on configuring SPAN and RSPAN on a 2950 can be found here:
http://www.cisco.com/en/US/products/hw/switches/ps4916/products_configuration_guide_chapter09186a008017e528.html
The only caveat is watch out for your aggregate throughput value. If you exceed the maximum throughput of the IDS, which is a mere 45 mbps for an IDS-4210 IIRC, you'll drop packets. If these are lower end links however, you should be OK.
I hope this helps,
Alex Arndt
