Getting Column Headers?

Ok, I'm being dumb.

I have 33 columns - only visible are 14 - displayed in a different order than loaded from the xml dataset.

I'm trying to read the visible column headings in the order that they are being displayed on the grid. I've tried various chunks of code to do it - but I must just be doing something really stupid.

I tried:

for (var P = 0; P < obj.getColumnIndices().length; P++) {
   alert (obj.getHeaderText(obj.getColumnIndices(P)));
}

Any help?
Thanks,

I guess it should be obj.getHeaderText(obj.getColumnIndices()[P])