Differential Backup question

Hello all,

I just installed the new Acronis Version 2014 and setup a weekly differential Backup Job routine.
My the question is:
Can I select the particular weekday, when the full Backup should be run?
I don't find this option.

For example I want to run a full backup on every Saturday and in between to next Saturday just differential backups. Can I setup this in that way?
I don't find the ability to say that the full back should hapen on the Saturdays.

Can anybody help me here?
I'd be very grateful for this.

Thanks in advance,
is