Multiple cell types

How can i make a cell both of type checkbox and read only??

You can’t mix types.
Of course it possible to create new excell type , which will combine logic from both excells, but there is more simple colution
Next code will make column with index == INDEX readonly, for any cell type

    mygrid.attachEvent(“onEditCell”,function(s,id,ind){
       if (ind==INDEX) return false;
       return true;
    })