[amibroker] Getting near the end

[John Bollinger]

Hello,

I'd like to change a calculation as I get within n periods of the end
of an array in real time.

if (BarIndex() <= LastValue(BarIndex) - n)
    do this;
else
    do that;

The above has problems as it compares an arrray to a number.

I've tried SelectedValue(BarIndex()).

TIA,

     jab