Change bottom bound of multiple frames.

I wrote a super basic script to change the bottom bound of any text frame from 10.7 to 10.75, but it isn't working. Where am I going wrong? Thanks!

var myDocument = app.activeDocument;


for(s = 0; s < myDocument.textFrames.length; s++) {    var bottomBound = myDocument.textFrames[s].geometricBounds[2];    if (bottomBound == 10.7) {        bottomBound = 10.75;        }    }