I am not aware of a way to directly limit the number of telnet sessions to the Cat5K with the software mentioned. Not sure what problem you are trying to solve, but you might consider these features in controlling/limiting access to telnet to Cat5K:
1) Make sure you have a terminal server to console on critical Cat5Ks (a 2511 for example), that way you can get on Cat5K remotely and use the disconnect command as necessary to remove telnet sessions from the Cat5K
2) set logout command -- use this to timeout sessions quickly once they are inactive
3) set ip permit command -- use this to control where telnet sessions can originate from, 4.5 version of command limits telnet and snmp, newer code versions allow the selection of snmp and/or telnet
