Protecting Selected Cells and Functions

Hi all,

I have a created a sizeable project which involves 3 different sheets with various dropdown selections, sort filters and formulas. I need to be able to protect the size of rows and columns, functions of the dropdowns, filters, cells containing formulas and fixed data cells but still allow the users access to choose from dropdowns, sort, and input data into blank cells when required. In short I have to make it as close to fool-proof as possible. I've had a look at various tutorials but nothing has really satisfied.

Cheers,

JLB.