AppleScript Error on Upgrade to Monterey – Mass SMS Text Application - macos

Question

Hoping someone can help with this – I'm running macOS Monterey on an Apple M1 Pro laptop. My AppleScript to send out batch text messages, stored on an Excel file, delivered through the Messages app is now not working – it worked fine on my old laptop operating under Catalina.
The problem appears to be in delivering the phone number ("targetBuddyPhone") into the proper location in the Messages app. Instead, the text message ("targetMessage") is being dropped into the recipient location in the app. Does anyone have any ideas on possible solutions?
Thanks in advance.
on run {input, parameters}
set phoneCol to "B"
set messageCol to "C"
set startRow to 1
set counter to "D"
set xlsFilePath to (path to desktop as text) & "texttest.xlsx"
tell application "Microsoft Excel" to open file xlsFilePath
tell application "Microsoft Excel"
set endRow to value of cell (counter & startRow) as number
end tell
repeat with thisRow from startRow to endRow
tell application "Microsoft Excel"
set targetBuddyPhone to string value of cell (phoneCol & thisRow) as string
set targetMessage to value of cell (messageCol & thisRow) as string
end tell
activate application "Messages"
tell application "System Events" to tell process "Messages"
key code 45 using command down -- press Command + N to start a new window
keystroke targetBuddyPhone -- input the phone number
key code 36 -- press Enter to focus on the message area
delay 3
keystroke targetMessage -- type some message
key code 36 -- press Enter to send
end tell
delay 6
end repeat
return input
end run

Answer 1

Since GUI scripting is always tightly tied to the version of the application, I recommend getting rid of it once and for all and using the following more durable solution:
on run {input, parameters}
set phoneCol to "B"
set messageCol to "C"
set startRow to 1
set counter to "D"
set xlsFilePath to (path to desktop as text) & "texttest.xlsx"
tell application "Microsoft Excel"
open file xlsFilePath
set endRow to value of cell (counter & startRow) as number
end tell
tell application "Messages"
activate
set SMSService to service named "SMS" -- YOU NEED THIS SERVICE
end tell
repeat with thisRow from startRow to endRow
tell application "Microsoft Excel"
set targetBuddyPhone to string value of cell (phoneCol & thisRow) as string
set targetMessage to value of cell (messageCol & thisRow) as string
end tell
tell application "Messages"
set theBuddy to buddy targetBuddyPhone of SMSService
send targetMessage to theBuddy
end tell
end repeat
return input
end run

Answer 2

I figured out the solution. To my GUI-based approach, I inserted delays into the script, which solved the problems.
on run {input, parameters}
set phoneCol to "B"
set messageCol to "C"
set startRow to 1
set counter to "D"
set xlsFilePath to (path to desktop as text) & "texttest.xlsx"
tell application "Microsoft Excel" to open file xlsFilePath
tell application "Microsoft Excel"
set endRow to value of cell (counter & startRow) as number
end tell
repeat with thisRow from startRow to endRow
tell application "Microsoft Excel"
set targetBuddyPhone to string value of cell (phoneCol & thisRow) as string
set targetMessage to value of cell (messageCol & thisRow) as string
end tell
activate application "Messages"
tell application "System Events" to tell process "Messages"
key code 45 using command down -- press Command + N to start a new window
delay 3
keystroke targetBuddyPhone -- input the phone number
delay 3
key code 36
delay 3
key code 36 -- press Enter to focus on the message area
delay 3
keystroke targetMessage -- type some message
delay 3
key code 36 -- press Enter to send
end tell
delay 6
end repeat
return input
end run
To Robert's solution, I changed one line (set SMSService to ...) and this script now works properly.
on run {input, parameters}
set phoneCol to "B"
set messageCol to "C"
set startRow to 1
set counter to "D"
set xlsFilePath to (path to desktop as text) & "texttest.xlsx"
tell application "Microsoft Excel"
open file xlsFilePath
set endRow to value of cell (counter & startRow) as number
end tell
tell application "Messages"
activate
set SMSService to 1st account whose service type = SMS -- YOU NEED THIS SERVICE
end tell
repeat with thisRow from startRow to endRow
tell application "Microsoft Excel"
set targetBuddyPhone to string value of cell (phoneCol & thisRow) as string
set targetMessage to value of cell (messageCol & thisRow) as string
end tell
tell application "Messages"
set theBuddy to participant targetBuddyPhone of SMSService
send targetMessage to theBuddy
end tell
end repeat
return input
end run