|Not sure I can get the stacking part in|
I can get
Y axis = minutes
X axis = Code
Series = date OR engineer but not both
I would need to tweek the spreadsheet a bit more if you are still interested, but I think excel lacks one more dimension for doing the type of graph you are envisioning.
So one graph can be total number of minutes spent on each code grouped by date, and the other can be the total number minutes spent on each code by engineer.
hrrmmm I suppose one could group the date and the code as an identifier for the X axis. Then you would get Code+ Date accross the X axis, things would then be grouped by engineer, and then have minutes on the X, and you can make an engineer called all that would be your total minutes. Still not what you were asking for exactly, but might work for you. Let us know.