I think you may create a custom command button "CMD1". You select a range, then click this button to submit the values. First, at the design window, right click the control and select "Custom Command Buttons...". Add a custom button, set it's Command property to "CMD1". And set it's image url.
Set the grid's OnSubmitClientFunction="OnGridSubmit".
Add the following script to the aspx file:
Hopefully, it will help you.