Thanks Gameer_77. And Hammy - the setdammage command does exactly that - set the damage of a unit to whatever number you want between 0-1. I wanted it to ADD 0.1 damage to a unit, not to SET it to 0.1.
Anyway, I was looking for more of a general command, I want any unit to get + 0.1 damage. Any ideas? Thanks for your replies everyone.