How to? Feed keys to firefox (Yahoo Mail) window

How would I do this please? I remember someone posted this before but can't locate it.

Thoughts so far:
= begin BTM
Goto :here

1 - switch to FF Window

2 - verify that Yahoo is in descrption

3 - feed Ctrl-A, M, zero, and delay of 15 seconds, repeatedly


= end BTM

Thank you in advance
If the FF "Yahoo mail" is already open - how would I change to it please, from the TCC window? Feed it Alt-Tab twice until

do until iswindow "*Yahoo Mail*"

is true?
So iswindow tests for the existence of the window:

do until iswindow "*Yahoo Mail*"
delay 1

:: window exists - now switch to it

activate "*Yahoo Mail*"

:: then feed the window.....

for /l %nRepeat in (1,1,100) (

keystack /w5 Ctrl-A /w5 "D" /w5 "0"
delay 20