blazed8 Without writing some bespoke software, EP can update stock levels and enable and disable products in the basic setup already (this does exclude Stock by Attributes works via a different database table/s).
In the last but one column in the complete file you will see v_status:
1 = Enabled
0 = Disabled
9 = Delete from database
Under v_products_quantity this the current stock available.
So using a table in OO or Excel you should be able to use your spread sheets !!