Header Menu

Iam trying to use the hide/unhide columns using the header menu (mygrid.enableHeaderMenu()). My grid has 9 columns and right now the header menu gives the option of hiding/unhiding all the 9 columns. But i would only like my users to hide/unhide columns from the 4th one. That is the header menu should only allow the users to perform the hide/unhide operation starting from the 4th column. Is this possible? If so please provide me with the relavent code.

You can modify dhtmlxgrid_hmenu.js in following way

line 69
    for (var i; i<this.hdr.rows[1].cells.length; i++){

can be changed as
    for (var i=4; i<this.hdr.rows[1].cells.length; i++){