Another Mouse Issue?

[NakedApe]

I'm working on a game, see, and I don't want the player to be able to hold down the fire-button indefinitely (that's cheating!). So I tried setting up a timer that kills the left mouse button after a second and a half. All is cool if the mouse is stationary, but the minute you move the mouse the button resets itself - without the user letting the button up - not cool. Is this a Mac mouse issue, a QB64PE mouse issue or a dumb NakedApe issue?
Is there a better way to do this?       

Thanks in advance for any insights, Ted

DIM AS _BYTE leftClick, started
DIM startTime AS LONG
SCREEN _NEWIMAGE(800, 600, 32)

DO
    WHILE _MOUSEINPUT
        leftClick = _MOUSEBUTTON(1) '
        mouseX = _MOUSEX
        mouseY = _MOUSEY
    WEND

    IF leftClick THEN

        IF NOT started THEN startTime = TIMER: started = -1

        IF TIMER - startTime > 1.5 THEN '    no holding the button down forever!
            leftClick = 0 '                              kill left click
            started = 0 '                                reset timer
            SOUND 1000, .7 '                         pip
        END IF

        _PRINTSTRING (380, 280), "Button Down"
        _PRINTSTRING (380, 320), STR$(TIMER - startTime)
    END IF

    IF NOT leftClick THEN '                            if buttonUP then reset timer and erase
        CLS
        started = 0
    END IF

LOOP UNTIL _KEYDOWN(27)
SYSTEM