A useful tip: if a similar indicator already exists, double click or right click the indicator, then look at how BC has written the formula in the "Formula" tab, then adapt it to suit your own purposes. You can of course make the above variable inputs.

 

You can do the same thing with a scan that you construct using BC easy language Create a Scan. When complete, click the tab 4 Advanced, then click Generate Scan Bullscript to see what it looks like in Bullscript...a great learning aid to help you write your own Bullscript.