Define a ‘prepareData’ function in the dataview object for the AttachGrid::DataView.

Something like this: 

prepareData: formatData.createDelegate()

formatData = function(data){
data.shortName = data.name.ellipse(15);
data.sizeString = formatSize(data);
data.dateString = new Date(data.lastmod).format(“m/d/Y g:i a”);
this.lookup[data.name] = data;
return data;
};

See --> http://dev.sencha.com/deploy/dev/examples/view/chooser.html more details.