Disable items in dialog object definition

Hello guys,

I would like to disable certain fields in the cell properties dialog when multiple cells are selected, specifically rowspan and colspan. What's the easiest way of doing this?

I would like to do it by using an inline conditional, e.g.

    type : 'text',
    id : 'rowSpan',
    label : langCell.rowSpan,
    'default' : '',
    validate : validate.integer( langCell.invalidRowSpan ),
    enable: cells.length == 1, // this is an example of how I want to make it work

Please advise.

Thanks,
Nitesh