This following AppleScript code should work if you save it as a “stay open” application.  Just set the property values for `scriptToRun` and `lookForThisText` and it should be good to go.

Don’t forget to grant permissions in System Preferences for your new stay open application to control your computer   


    property scriptToRun : (path to desktop as text) & "your.scpt" -- your path to .scpt file
    property lookForThisText : "Search For This Text In Notification Windows" -- your search term
    property theseTitles : {}
    
    on idle
    	getNotificationTitles()
    	delay 0.1
    	if theseTitles contains lookForThisText then
    		---------------------------------------------------------------
    		delay 6 -- Gives Banner Time To Self Close
    		--tell current application to beep 5 -- Just For Testing
    		run script alias scriptToRun
    		---------------------------------------------------------------
    	end if
    	return 1 -- in seconds
    end idle
    
    on quit
    	--	Executed when the script quits
    	continue quit -- allows the script to quit
    end quit
    
    on getNotificationTitles()
    	-- This Gets The Titles Of The Currently Displaying Notification Alerts And Banners
    	tell application id "com.apple.SystemEvents"
    		tell (the first process whose bundle identifier = "com.apple.notificationcenterui")
    			set theseWindows to every window whose subrole is "AXNotificationCenterAlert" or subrole is "AXNotificationCenterBanner"
    			set theseTitles to {}
    			repeat with thisWindow in theseWindows
    				set titleText to the value of static text 1 of thisWindow
    				set the end of theseTitles to titleText
    				set subTitleText to the value of static text 1 of scroll area 1 of thisWindow
    				set the end of theseTitles to subTitleText
    				set notificationText to the value of static text 2 of scroll area 1 of thisWindow
    				set the end of theseTitles to notificationText
    			end repeat
    		end tell
    	end tell
    end getNotificationTitles




- - - - 

Here is a quick animation showing the process in action.  I created an AppleScript app named Test Notification.app whose only purpose is to display a notification… `display notification "Blah" with title "BLAH BLAH" subtitle "DUH”` Then, using the code I used as the answer to this post, I created a “Stay Open Application”, whose only purpose is to monitor all incoming notification windows for the text in which I define in the variable `lookForThisText`.  Once the text is identified, it triggers another script "Merge Every Finder Window.scpt" which as the name says… merges every Finder window.

[![enter image description here][1]][1]

[![enter image description here][2]][2]


  [1]: https://i.sstatic.net/gG3Fx.png
  [2]: https://i.sstatic.net/LeIwB.gif