Hi,
I've been developing .NET applications, mostly using MS SQL, for past several years and would like to help you with the project. Similar problems to yours often arose, offcourse, it's a question of data complexity how fast and for which price it can be handled, but I'd like more details before giving my final bid: as much as you can disclose about the data structure, which library is used to work with Excel and what are the business rules for updating/creating/deleting records (how the record in excel file is mapped to a record in database: by primary identifier or by some other rule) etc. Only after getting to know these specific details would I give my final offer.
Kind Regards,
Vladan Stojanovic