I’d like to suggest you to utilize the “OnBeforeRequest” client side event. OnBeforeRequest client side event specifies the client side (Javascript) function that will be invoked when request action to server is about to be made.

Below is the snippet code that shows a simple sample of script that iterates through all the cells of WebGrid filter row and obtain its inner text.

<script language="javascript" type="text/javascript">
    <!--
    function WebGrid1_OnBeforeRequest(controlId, action) {
        var WebGrid1 = ISGetObject(controlId);
        var rootTable = WebGrid1.RootTable;
        var filterRowEl = rootTable.GetFilterRow();
        var filterRowLength = filterRowEl.cells.length;
        var i = 0;

        for (i; i < filterRowLength; i++) {
            var filterText = filterRowEl.cells[i].innerText;

            //your validation code in here
        }

        return true;
    }
    -->
</script>

Hope this helps.

thanks Yudi, just what I needed.

Glad to hear that the information helps.

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