The paste operation is not allowed on numberbox. To enable the pasting feature, rebind the 'paste' event on numberbox after calling 'beginEdit'.
$('#dg').datagrid({
onClickRow:function(index){
$(this).datagrid('beginEdit',index);
var ed = $(this).datagrid('getEditor',{index:index,field:'unitcost'}); // get numberbox editor
$(ed.target).unbind('paste.numberbox').bind('paste',function(){
return true;
});
}
});