When using MM_setTextOfTextfield with the datagrid how do take a cell value from the grid and populate into a text field?

I've tried this to no avail:

onclick: "controlAjaxDataGrid(document, 'dmx_grid13', 'setFilter', 'custom', 'Lead ID', '=', '{lead_id}');MM_setTextOfTextfield('lead_id','','\{Lead ID\}');"

Also, is there a way to pass information on click into a hidden field?

I got standard it to work. The issue was that I could only pass on variable in the oncick routine. I did a mouseup routine and it works fine now.