Using keyboard shortcuts
To insert subtotals within a range of cells:
1. Select row 4, then press Ctrl++ (the + sign) to insert a new row.
2. Select cell A1, then select the Current Region by pressing Ctrl+Shift+*(in Excel 2003, press this or Ctrl+A).
3. Press Alt+= or click the AutoSum icon.
4. Select any cell within the data area, then select the Current Region by pressing Ctrl+Shift+*, and repeat step 3.
5. Repeat the previous step after selecting any cell within the data area, (that is, select the Current Region and then repeat step 3).
Row 4 now contains SUM formulas for the data in rows 1:3, row 9 contains SUM formulas for the data in rows 5:8, and row 10 contains only the SUM formula for the two subtotal formulas (note that the formula in cell C10 is =SUM(C9,C4). Screenshot // Inserting Subtotals Quickly