Hi,
I come from a corporate background, and I understand the need to create China walls around critical information. I have encountered many situations in the past where I had to create such segregated information databases. Hence a simple locking of your excel sheet will not be sufficient. Fortunately the newer version of excel allow additional fail-safes to be built in to protect your underlying data. e.g you can not only hide a sheet, but you can also [veryhide] it. A very hidden sheet, needs a macro to execute and unhide those sheets, Making it tougher for unauthorized access. There are a couple of more such tricks which can 1> Stop unauthorized access
2>Help deter unauthorized access
3> track unauthorized access
While also ensuring that required data is visible to those who need it.
Your project needs someone who can not only understand your requirement, but also preempt your security needs, and I believe I am the right person. I have over 10 years of experience working with companies like A.C. Nielsen, Pratt and Whitney, Accenture, Volvo.. So I can be a great asset, not only for this requirement, but also future requirements.
As with any good service, there is a cost associated. So has mine. Ofcourse you can try the £20 bidders, and hopefully not waste your time, or you can chat up with me, and I will be happy to address any concerns or queries you might have.
Regards
Amin