Hi WangNi, you can use the Auto Refresh widget, here are the steps:
1. Bind the service getting all the data for your Grid Widget
2. Drag and drop the Auto Refresh widget on the mashup, and bind it's Refresh event to the service getting all the data for your Grid something like this
3. If you don't want to show the auto refresh widget on the mashup you can disable it's visibility from the Widget properties section
As you can see default value for auto refresh is set to 30 secs you can change as per your requirement. Chain of events will be something like this that once the auto refresh refreshes itself Refresh event will be fired which is tired to the service getting all the values so it be fired again to fetch the values so here's how the overview looks like for the GetPropertyValues which i used in my sample mashup to show this
Hope this helps.