Subscribe to rowSelected event from iframe parent window

Hello,
I have an AJAX control which contains an IFRAME which load a page and grid on it. Like this:
parent page -> AJAX control -> IFRAME -> grid
I'd like to subscribe grid's rowSelected event from my control. That's what I do:
1. Searching for grid:

this._grid = this._frame.contentWindow.$find(this._frame.contentWindow.gridID);
if (this._grid != null) {
            this._grid.add_rowSelected(this._onRowSelected);
        }

_onRowSelected: function (sender, args) {
    },

this._grid object in my control is a valid grid object so it must start my handler when event fires. But it never starts. I tried to subscribe rowSelected event within page in iframe and it works fine. What's wrong? Is that because grid and my control are on "different" pages? I quote this because they're all defined within a single DOM and they should "know" about each other.
Please help.