So, I'm trying to Install Arena on my new laptop, and when I attempt the 'C:' command only 'C;' comes out. I go to the keymapper (ctrl+F1) but I cannot figure out how to add the colon event, and my : button is only listed as the ; event. Any ideas?

I have managed a workaround by adding the commands to the autoexec part of the config file. I'd still appreciate any other help.

You should be able to change between several keyboard layouts in the dosbox.conf file.
Near the bottom, above the autoexec part you have this line:
keyboardlayout=
For Norwegian that would be:
keyboardlayout=NO
Change it to whatever the standard abbreviation for your country is; FR for France, US for USA etc.

Note that this does not work with any language. You could try searching for a list or something.

I figured out the problem. Since I last used dosbox, there was some kind of keyboard update that only accepts left shift as the 'mod2' action. Before it had been right shift or both, I don't recall. So when I wanted the colon and went to use 'right shift + ;' it resulted in nothing. Using 'left shift + ;' = colon now. I don't know why they would have changed it. Also, this can be changed by assigning both right shift and left shift to mod2 in the mapper.