I am impressed by all the suggestions mentioned above. I could use some of that myself, but when it comes to my students it has to be very robust. Some students are pretty good at mathematics and physics, but get scared by too much code and workarounds. This is in particular the case for some of my female students.

John May: I tested your maple file. Try pressing the "Execute the entire worksheet" button. This will show that your "startuprun" variable defined in the Startup Code Region is only being assigned the value true before the first restart. That's at least how it works on my machine using Maple 14. I really wish it had worked, because it would have been a pretty nice and robust solution. If just Maplesoft would extend the functionality of the Startup Code feature, so it will work after the first restart ...

Erik     

Maybe I need to redefine the dimensions without units and plot the graph and then put labels on manually:

> plot(A(t), t=0..100, labels=[t [[years]], A [[Bq]] ])

I can make it work this way, but it is annoying this is necessary ...

Regards, Erik V.

Sorry for not answering earlier. Your suggestions works perfectly, both import from Excel and the readdata command. Thanks a lot!

Regards, Erik V.