I have a IRADV6255 in a customers and they are printing from an IBM I series system to the machine

they have the same paper in all the trays and would like the machine to auto switch from one tray to another, unfortunately the I series sends the job to a specific tray and so the Canon will not tray switch when it is empty due to the print going to a specific tray.

does anybody know how to set the I series to select tray automatically as this seems to be the only way round this issue.

thanks in advance!