planning incremental backups

Hello,

i want to plan a Backupjob for Fullbackup and incremental backups that alternate every 4 weeks. I have 4 Jobs which perform a Backup-to-Disk backup on 4 different folders. I could plan the fullback by planning the backup to be run every 28 days. But how can i plan the incremental Backups from Monday to Thursday to run every 4 weeks?

regards,

Joachim Kühne