How can I pass script object as a parameter in apple script

AppleScript
#1 
script WordShortcutKeys
    on OpenDocument()
        tell application "Microsoft Word" to activate
        tell application "System Events"
            keystroke "o" using {control down, command down}
        end tell
    end OpenDocument
    on SaveSyncDocument()
        tell application "Microsoft Word" to activate
        tell application "System Events"
            keystroke "s" using {control down, command down}
        end tell
    end SaveSyncDocument
end script
set application_name to  "Word" & "ShortcutKeys"
application_name's SaveSyncDocument()

It shows below error
error ““WordShortcutKeys” doesn’t understand the “SaveSyncDocument” message.” number -1708 from “WordShortcutKeys”