Will iCal be able to help me in this case, and how?

I have a maid who will clean my condo twice a week. I pay her at the end of her 4th week (8th times). I can easily schedule an event on iCal to alert me a couple of days before that 8th day since it will be the exact same day of the week.
But she may ask me for a day off and then everything will change. So now she will not work on, say, Monday but will begin instead on Thursday. This way the day I pay her will be moved to different day of the week. Now I know I can move the event and all afterward a few days after but will the alert also moves? And how exactly to set the alert?

ApfelKuchen said:

The alert normally changes when you change the date/time of the event. You'll note that alerts are normally scheduled "5 minutes before," "1 hour before," "1 day before," etc. ONLY if you use the Custom alert feature and select "on date" will the alert not change if you change the event info.

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So if I don't use custom alert, just 1 day or 2 days before, it will work?

ApfelKuchen said:

Yes, and you can even use Custom Alert options, except for "On Date..."

This is the whole point of the minutes before/hours before/days before approach - if you change the event date or time, the alert(s) automatically adjust.

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Great. Many thanks for the help.