Without the conditional macro option, you could set up the timer events to only happen on specific days. These are what AHP calls "holidays". There is a option that allows you to change these to any days you want, including your planned vacation days. They don't need to be, at all, only legal holidays.
However, if you want to get the conditional macro option, you could use "flags". You would set up one of the flags to mean "I am on vacation". You could set up a conditional macro, that would test for "I am on vacation" to be true, and only then turn lights 'on' and 'off'. You would then set up this macro to be triggered on a timer.
Also, you would need to set up a pair of macros that would either SET or RESET the "I am on vacation" flag. You would just need to remember to execute that macro.
I, myself, use the flag method. However, I always seem to think of running the "I am on vacation" flag setting macro when I am at the airport. I, then, call up one of my friends who has X10, and ask them to drive over to my house with a manual controller, plug into an outside outlet, and do a F10 'on'.