This here is what I use most of the time.
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bind ctrl "+QCOn"

alias +QCOn "bind MOUSE1 "M1"; bind MOUSE2 "M2"; bind MOUSE3 "M3"; bind MWHEELUP "MU"; bind MWHEELDOWN "MD"

alias -QCOn "bind MOUSE1 "+attack"; bind MOUSE2 "+attack2"; bind MOUSE3 "+attack2"; unbind MWHEELUP; unbind MWHEELDOWN"

alias M1 "voicemenu 1 0" // "Incoming"
alias M2 "voicemenu 1 1" // "Spy!"
alias M3 "voicemenu 1 2" // "Sentry Ahead"
alias MU "voicemenu 2 6" // "Nice Shot!"
alias MD "voicemenu 2 7" // "Good job!"

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What this does is bind the left ctrl key to toggle "+QCOn" which bind all mouse keys to various voice commands. As you see on the bottom aliases, their named after the key. So mouse1 is "Incoming!" and mouse2 is "Spy!". Once you let go of ctrl it rebinds all of the mouse keys back to normal (well normal for me).

You can use this yourself and can swap out the "voicemenu # #" to whichever lines you want you character to yell out.

Copied from the TF wiki because I'm lazy.

voicemenu 0 // Default bind is Z

0: MEDIC!
1: Thanks!
2: Go! Go! Go!
3: Move Up!
4: Go Left
5: Go Right
6: Yes
7: No
8: Pass To Me!

voicemenu 1 // Default bind is X

0: Incoming
1: Spy!
2: Sentry Ahead!
3: Teleporter Here
4: Dispenser Here
5: Sentry Here
6: Activate Charge!
7: MEDIC: ÜberCharge Ready
8: Pass To Me!

voicemenu 2 // Default bind is C

0: Help!
1: Battle Cry
2: Cheers
3: Jeers
4: Positive
5: Negative
6: Nice Shot
7: Good Job