Help with macro, please...

[DoctorPepper]

You need to press the button only once, and not use any other spells before aero goes off. The macro with wait 3 will cast bio, wait 3 seconds, then cast aero. If you use any other spells during the wait it will cancel the macro, if you press the button a second time it will cast bio again and start the macro over. Bio and Aero really are not good skills to macro together since you cannot rely on not needing to interrupt the macro occasionally.

Generally for macros you want to use them for abilities with cooldowns or for abilities that work off of the global cooldown.

For example, on bard you can make the following macro:
/ac "Heavy Shot" <t>
/ac "Misery's End" <t>
/ac "Bloodletter" <t>

Spamming this macro will always use heavy shot when the global cooldown is not active. When the global cooldown is active it will use misery's end first and if it's on cooldown or not useable it will use bloodletter. This ensures that you are not using those 2 skills that work during the global cooldown when the global cooldown is not active, increasing your overall dps.

Additionally if you are using several abilities that have long cooldowns, such as buffs, you can macro them in order of how you want to use them and spam a single button for that as well. For example, you could make a macro for bard like this:
/ac "Hawk Eye" <me>
/ac "Raging Strikes" <me>
/ac "Barrage" <me>

You can add/remove abilities to that macro but because all of those abilities have long cooldowns, pressing that macro multiple times will use the skills in order depending on whether they are on cooldown or not.

I hope that gives you a better idea of the useful application of macros, pairing bio/aero together in a macro is not recommended.

One that I use on smn/sch I call eye virus. It casts virus if your target is a monster and casts eye for an eye if your target is a party member, it looks like this:

/micon "Eye for an Eye"
/ac "Eye for an Eye" <t>
/ac "Virus" <t>