jQuery Grid Plugin - jqGrid

I want the cells to be in edit mode when a certain condition is true. I'm using cellEdit true and editable in the column but in some occasions the user shouldn't be able to edit some cells of the same column even though the column is editable=true. I need to use cell editing not inline editing.

I tried with beforeEditCell:

beforeEditCell: function(rowid, cellname, value, iRow, iCol) {

                 //Some conditions here that I validate before making the cell non editable
                jQuery("#miGrid").jqGrid("editCell", rowid,iCol,false);
            }

It didn't work and the the cell still editable.

Any thoughts?

Thanks in advance.