Capture reaction time to specific button press

I would like to measure how long it takes a user to press key 1 after display of an instruction key. I've tried using tic toc but from manually checking elapsed time, I know that the variable 'reaction' is not capturing the data correctly. Are there any other ways I could do this other than tic toc? Thanks

one=KbName('1!');
Screen('DrawText',win,'Please press 1',100,100)
Screen('Flip',win)
tic;
while KbEventAvail;
    [evt,n]=KbEventGet();
    if evt.Keycode==one & evt.Pressed==1;
        reaction=toc;
    end
end

Answer 1

[LG]

I've found a solution through the following. Hope this helps others :)

one=KbName('1!');
Screen('DrawText',win,'Please press 1',100,100)
Screen('Flip', win)
onsetTime=GetSecs;
while KbEventAvail;
    [evt,n]=KbEventGet();
    if evt.Keycode==one & evt.Pressed==1;
        reaction=evt.Time - onsetTime;
    end
end

Answer 2

[David Hill]

Take a look at my Psychomotor Vigilance Task code:

https://www.mathworks.com/matlabcentral/fileexchange/106625-psychomotor-vigilance-task-pvt