For this you will want to create a group and put the computers you want to target in the newly created group. When you are creating your subscription you can then select "raised by any instance in a specified group" and "created by specific rules or monitors" and then select your newly created group and select the desired rule(s)/monitor(s). Clicking on the blue "specific" links at the bottom will allow you to choose the desired group and rule(s)/monitor(s).
I hope this helps!