out of support from CA but must not be difficult to accomplish that by modifying the msg_catalog.
this is a pure js.file so you can code your logic directly there and overwrite default using the msg_cat_site.js file that you will put inside your site/mods.
In your case the message you are looking for is mostly: __messages["Save_Successful"]="Save Successful";
Then you will create your logic there something like the pseudo code below that you can extend to match your needs.
//retrieve the associated incident list
<PDM_LIST ESC_STYLE=JS2 PREFIX=listprinterticket FACTORY=in WHERE="delete_flag=0 and z_printer_code= $args.z_printer_code">
</pdm_list>
var zTicketLength = listprinterticket.length;
if (type == "I" && zTicketLength >1 ){
__messages["Save_Successful"]="Warning there is already tickets for the same printer!";
}
else{
__messages["Save_Successful"]="Save Successful";
}
the only downside I see with this approach is that the list returned will be the one at the time the page is loaded (preprocessor engine).
Then if someone create a ticket with this attribute in between you save, this will not be taken in consideration.
Hope this help,
/J