I have already replied in the official support ticket which you have opened regarding this matter. In order to help other community members to overcome this issue I am posting my reply here:
"The functionality mentioned is achievable by ajaxifying the RadGrid and subscribing to the client OnResponseEnd event of the RadAjax which will be used for opening the RadWindow. The idea is to intercept the server-side OnClick event of the button and execute the logic for saving the information in the database there. Once the response from the server comes back you can check which control initiated the postback and if it is the button open the RadWindow. A sample demonstration of this can be reviewed in the attached website."
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