The ability to coordinate the throwing of multiple potions to have them land together or close together was removed years ago. When using UOA, as far as I know, each have to be thrown before the next one can be "loaded". It may be possible using another program, but I was able to do this with UOA. There is also a 1 sec delay between using actions in UOA. This is eaten up by the delay in throwing if you set one.
Having said that, you have several targeting options.
1. You can target a specific tile. Wherever you stand, the potion will hit that tile. However, if it's out of range, it will explore in your hands.
2. You can target a specific tile *relative* to your position. - say 4 tiles to the East. I don't think that the relative targeting takes account of facing which is a pity.
3. Finally, you can target a specific player. This is a little more complicated. If you were always to be targeting the same player, you can add them as a target. If you change targets, you will have to reset the target in the macro. However, if they are out of range...etc Alternatively, you can set Target Last Target to a separate key as many do in pvp and just load the pot then press your last target key. Unfortunately, this means a separate operation for each potion.
BTW, it's really worth trying to fit alchemy into your template if you are planning on lots of Explo pots.;p
Be happy to hear if anyone has anything to add to this. I tested it all some years ago and may have forgotten/left stuff out/be wrong or out of date.