Most likely you won't be able to do it the way shown in your example, but I have created another way to solve your idea.
You can try using this variant of the script code:
on *:TEXT:*:#:{
if ($var($+(prefix_,$chan),1).value isin $1-) {
msg $chan Found dynamic variable with name04 $+(%,prefix_,$chan) and value:04 $v1
}
}
Note: This script will only run if you have a global dynamic variable saved in your mIRC (for bot) with the name of the channel where a message was sent by another user whose text matches the text value of this variable.
For example, enter this command in your bot's #test channel window:
//set -s %prefix_ $+ $chan New trigger text
This will create a global dynamic variable with the channel name "
%prefix_#test" and the value "
New trigger text" as an event trigger.
Screenshot of testing the script: