No it's an assignment, although It is a fun challenge. Otherwise I would of used a PIC microcontroller interfaced with a keypad and programmed it with assembly. Unfortunately its much more complicated than that.
Well, I suppose you have to work within the constraints imposed by your customer (or worse, your boss). Maybe you can make a pitch for the PIC microcontroller + keypad idea, and if that is acceptable, save yourself a lot of time and effort.
Try the SN54AS109A series of positive edge-triggered J-K flip-flops. See attached data sheet. Note the K input is active low while the J input is active high. That means if you tie the two together it acts like a D-type flip-flop.