[ILUG-BOM] Blocking telnet on a specified condition

I want to know how I can block telnet access to my machine _when_a_specified_condition_is_true_.

I have a lot of people telnetting to my m/c (in office) and then they run some heavy processes. As per the rules and requirements of the project, I'm not supposed to block telnet access completely. But under certain circumstances, I can block telnet access. The "certain circumstances" can be a set of rules. For example, if load average (w|head -1|cut -f3 -d,) is greater than some limit, or if the amount of free memory (free|tail -1|tr -s ' '|cut -f4 -d' ') falls below some limit, or something like that.

I'm clueless, so... please help.

Manish