Hiding cells after a certain sequence

[woweee]

Hi

I am very new to Excel and wondering if Excel can do this

I have a string of negative and positive numbers in a row which are being totalled.

1. When there are two consecutive cells containing negative numbers I want the second cell and any additional consecutive cells with negative numbers hidden. Hidden numbers not to be included in the total.

2. When the consecutive negative numbers are followed by a positive number the positive number is also hidden.

3. After the second positive number the system is reset and waits for the next two consecutive negative numbers.

Example

£22
-£25
-£11 Hidden
-£12 Hidden
£65 Hidden
£31

Total £28.00.

Thanks for looking
Mike.