Grouping Sheets

Hi,

I am building a database of suppliers for a company. There are 35 categories for example Brickwork,fencing, roadwork,architects etc.

Currently I have a summary sheet and 35 sheets open, each with a list of suppliers details. The 35 sheets fall under 7 main categories ie Internal, external, Professional services etc.

Is it possible to see 7 tabs at the bottom (main categories) so it's not too clustered, then when I click on say professional services i expands to show the underlying 5 subcategories.

Kind of layering/grouping the sheets.

Hope this is clear!

Thanks

Joe