I'll recommend that you use $addtok() $remtok(), and $istok()

set %block $addtok(%block,#,32)

to add channels.

set %block $remtok(%block,#,1,32)

to remove channels.

Then use:

on *:text:*:#:{
if ($istok(%block,#,32)) { halt }

This way you don't waste var space when you can store the values from left to right.