Required library edition:
Required library file: dhtmlxgrid.js

indicates whether the cell is disabled by method setDisabled. Returns true if the cell is disabled. Otherwise, false.
If setDisabled wasn't called for the cell, the method returns 'undefined'.

Returns: boolean

mygrid.cells("row1",4).setDisabled(true);
...
mygrid.cells("row1",4).isDisabled(); // ->true

See also: setDisabled