I am using Quickload. North American distributor is here: http://www.neconos.com/details3.htm
I use it to compare loads. I never use it to develop a load, which is different to what the loading manuals say.
I found a spreadsheet on the net that was so-so, modified for my use, added a nice trajectory graph (like those graphs). As for loads, I just label my plastic boxes and adjust as necessary. Playing with MS Excel is a hobby and more in the engineering field.