display date range in grid

Hi,

I'm try to build an app where users can order rooms in some hotel. And now I have some troubles with display date ranges in Grid.

Code:

{
"data": [
    {
"id": "1",
"room": "100",
"checkIn": "2014-12-17",
"checkOut": "2014-12-28"
},
    {
"id": "2",
"room": "101",
"checkIn": "2015-01-09",
"checkOut": "2015-01-10"
}
  ]
}

It's part of my json.

grid.jpg

And how I can group cells that is in date range? I'm try to do something like Calendar in examples. I'm very new in ExtJS and I'm stuck with this.

Any help please. Thx.

display date range in grid