How to get visible rowindex of aspxgridview on row deleting event

The solution was the PreRender event:

protected void ASPxGridView1_PreRender(object sender, EventArgs e) {
        if(!IsPostBack)
            ASPxGridView1.FocusedRowIndex = -1;
    }

This can be done using the ASPxGridView.GetRow() method. NOTE, that changing the value in the DataRow is not enough. If you want these changes to be preserved, save them to the DB.

Since you are using unbound columns, you should handle the CustomUnboundColumnData event and provide modified data for this row within this event handler. The common approach is described in the Providing Data for Unbound Columns topic. If this does not help, please describe in greater details.

UPDATE

Your approach is incorrect. The ASPxGridView does not provide a method to set a text of a certain cell (TD). Instead, you should force the grid to raise the CustomUnboundColumnData event. This can be done using the ASPxGridView's DataBind method. In this event handler, you should determine the KeyField value of the processed row, compare it with the keyField value of the row where the button was clicked and return the required value. This is how I would implement this feature...