Make certain status forbidden when a particular status is active

Hi Gurus,

I need to make certain status forbidden and not available when a particular status is active. For instance, the highest status from status number 20 is status number 80. However, I do not want customer to be able to activate any of the status between 20 and 80.

Tried with transaction control without much help. Could anyone please suggest how to get this done.

Thanks in advance.

Aershid