Try this script, the timing is not precise, you may want to do some work on that.
@echo off
cls
setlocal enabledelayedexpansion
for /l %%1 in (5,-1,1) do (
echo !time:~0,-3! aaa.txt is waiting %%1 second(s^) to startup...
ping -n %%1 -w 100000 127.0.0.1 > nul
)
start /b "" c:\aaa.txt
exit