IF your manually coded sub-totals use the subtotal function then the grand total will be unaffected by the sub-totals. However your example suggests that this is not the case, so:
If you have another column that can help to identify the sub-totals then you can use that to filter out these existing sub-total rows. (Use autofilter with, for example a custom criteria "does not contain "total" or to filter for blanks in one column but non-blanks in the column to be totalled).
The subtotal function applied to the entire column will show the total of the visible rows only and thus enable you to check the grand total ("overall result"). Equally the filtered total can be made to display in the statusbar.
OR (xl2003)
Select the column of data,
Edit,GoTo,Special,constants
view the total of selected cells on the right hand end of the Status Bar
(beware if some of your data is actually a formula like = 100+75 it will not be identified as a constant. (Hold down Ctrl to add to your selection manually.)
OR, if you are lucky with your data layout, the autosum function will create a good sum(...) formula.
Use goto,special to select formulae,
then click the autosum button.
Remember you can copy the column to play with without ruining the existing data. Once you have good formulae in this working column you can delete all the constants so you just have the formulae in the column and then Copy, PasteSpecial, SKIPBLANKS over the original.
Gavin