Following is my trick to apply AutoSUM for multiple Rows and Columns.
*Select the entire data range with an Extra Column and Extra Row
*Press ALT + =
If you have multiple worksheets with similar data ranges, groups the sheets and apply the same trick.
*Select the first sheet containing data
*Holding the Shift key, select the last sheet containing data
*Select the entire data range with an Extra Column and Extra Row
*Press ALT + =
