Advanced Dungeons & Dragons 1e - Dual Classing

I just started playing around with the character sheet. I must be obtuse but I can't seem to figure out how dual-classing works from a hit point/hit dice standpoint.  I understand how it calculates demi-human multi-classing but I can't figure out if there's a switch or setting that will allow dual-classing.

Hi Stewart, there isn't anything on the sheet specific to being dual-class.  HP is entered however you like per class row in the Class Details section.  The sheet will auto-calc total HP based on the three available class rows.  Obviously this is set-up more for multi-classing but I'm not sure how this wouldn't work for a dual-class character as well as long as you only entered the appropriate value in the HP column for a given class/level.  I'm open to suggestions though. Cheers

Thanks.  I'll deal with it by manipulating the HP for each class to come out with the number it should be. Not a problem.  Thought I must be missing something since I'm new to the character sheet so I figured I'd ask.