I need an excel costing schedule creating with auto sums

We have a very basic series of excel sheets with costs against certain criteria and we use these to calculate quotations for clients. However, I require the excel sheets to become much more automated with functions and sums. We need to be able to type in the opening dimensions and the sheet to calculate automatically how many panels are needed (based on certain 'what ifs'). Then, it needs to pull together costs of various elements that make up the offer to our client (so we type in veneer finish and it needs to pull the veneer 'per panel' rate and add it, then we state install in London so it needs to pull the 'install in London' rate and add it.

We have 4 or 5 of of these we need doing, for each different system we sell.

You can see our moving wall systems by visiting our website: www.creatif.org.uk

Thanks.