Summer grasses / All that remains / Of soldiers' dreams. - Basho.
You can attempt to Tally before you reach the vector location.
Essentially, as long as the squadron is not Broken and not required to keep an existing tally, you can attempt a new tally in the tally phase.
Jim has it.
Similarly, Escort-mission squadrons/flights can try to tally incoming interceptors instead of just reacting when they go into attack. This is especially important when the incoming fighters are angling for a head-on attack, which is pretty frequent.