Pinpointing Tertiary Progressions

Hi all,
I've just started checking out my tertiary progressions (fascinating stuff! ) and wonder if there's a way to pinpoint the day of an exact aspect as I do with other transits and secondary progressions. For me, events and circumstances always occur on the exact day of the transit (with transits more than progressions, of course), but I'm trying to pinpoint the day or week my tertiary mercury will square my natal sun. Astrodienst will only show tertiary charts with a one-month window. Any pointers? Or will I need to buy a program?
Thanx!
Neo

You're going to have to get real software to use. There's no excuse, because there's plenty of freeware out there. Astrowin is one you can use. Otherwise, you'll have to do the calculations by hand.