Not like that, no.
Not that you have any need to. Here’s a modified version of your code:
property theMagFolders : {¬
{magName:"AA", lastUpdate:""}, ¬
{magName:"AL", lastUpdate:""}, ¬
{magName:"AR", lastUpdate:""}, ¬
{magName:"DR", lastUpdate:""} ¬
}
tell application "Finder"
set thePath to the folder "merion_image_archive" of folder "Cumulus_Test"
repeat with magRec in theMagFolders
set modDate to modification date of the folder magRec's magName of thePath
if modDate = magRec's lastUpdate then
display dialog "There have been no changes to the folder " & magRec's magName
else
display dialog (modDate as string) & return & "There have been changes to the folder " & magRec's magName
--do cumulus scripting stuff here
set magRec's lastUpdate to modDate
end if
end repeat
HTH