Heres a few of suggestions......
If you buy the three of em.....Tell him the second one was half price and the third one free, because you bought the other two.
OR
Tell him you only bought one, stash the other two away, and just bring them out one at a time,and tell him its the same one....men dont notice the different patterns and designs on them.
OR
Tell him it is last years shirt
OR
Tell him a friend sent them to you.
OR
Tell him that you were talking to someone in the horsey comptetion and that extra points will be given for exceptionally nice outfits.
OR.....if all else fails......
Squeeze a tear or two out of your eyes, and tell him you just wanted him to be proud of you in such a lovely outfit, and you wanted to buy them more to make HIM happy, than yourself.
OR......(but this is only if you want to start World War Three)
Put your hands on your hips (which from what ive noticed, you do fairly often), and say " F*** YOU, IM GETTIN EM...."
Once you have placed the order, with his blessing......THEN AND ONY THEN, you can do what Fiona (Optom) suggested.