Backup mailbox of mail.app with applescript

I would like to automate, with applescript, the back up a mailbox of mail, which is manually done with the menu "Export mailbox ...", but: I can not set the folder where the mailbox will be saved; I can not set the mailbox to export, it works only with the mailbox that I've previously selected manually with the following command: Click menu item...

The lines of the script, which does not work, are:

tell application "Finder" --set mboxSavePath to "HD Macintosh:Users:simonepiersigilli:Desktop:e-mail:" -incorrect command to set the save path- --set mboxSavePath to "/Users/simonepiersigilli/Desktop/e-mail/" -incorrect command to set the save path- --set path POSIX to mboxSavePath -incorrect command to set the save path- end tell tell application "Mail" to activate tell application "System Events" tell process "Mail" --click menu item "cesare@appuntidigitali.eu" of menu "Entrata" of menu "Caselle" of menu bar 2 -wrong command to set the mailbox to export- click menu item "Esporta casella di posta…" of menu "Casella" of menu bar 1 -correct command to open the menu "Export mailbox ..."- -- Now click the Go (choose) button click button "Scegli" of sheet of front window -correct command to click the button choose- tell application "Mail" to close the front window end tell end tell

Can anyone help me? Cesare