I searched the web, found a graphical Excel sheet for a TB20 and converted the sums to metric, modified it with the correct limits and envelope, hey presto, a graphical representation plus little "if greater than" alarms if I go overweight or out of the w&b envelope.
The 172 I fly has simpler limits, mostly MTOW and so I made up a little postcard size "manual loadsheet" and do the calcs on in a couple of minutes with a little "x" on the w&b graph beneath.