F1:: time := A_TickCount

F2:: msgbox, % "Прошло времени: " FormatTime(A_TickCount-time)

FormatTime(Time) {
	Local Rest, Hours, Min, Sec, MSec
	If Time < 0
		Return "00:00:00"
	Rest := Mod(Time, 3600000)
	Hours := Format("{:02d}", Time // 3600000)
	Min := Format("{:02d}", Rest // 60000)
	Sec := Format("{:02d}", Mod(Rest, 60000) // 1000)
	; MSec := Format("{:03d}", Mod(Rest, 1000))
	Return Hours ":" Min ":" Sec
}