Budget Woes and making Excel switch negative numbers

I've been in some financial training today... all great fun and it really allowed me to explore IT outside of my normal domain.

However they have some weird habits these accountant folk - and their terminology is more obscure than mine... GL, PL, General Ledger, Code, Cost Centre, Budget, Plan, budget accounts... all great fun, but they also get quite picky about their negative number representations in Excell, and Excell can be very annoying with text formatting and numbers and sometimes completely ignores your instructions - especially in respect of CSV files.

We needed to take some Incomes and make them negative... how counter intuitive is that... however I proved my usefulness by converting the entirety of one of their Worksheet of Incomes to negative numbers.

Place a -1 in a cell and copy it.
Highlight all the numbers you'd like to reverse.
Edit -> Paste Special

Choosing Multiply and Values on that pane.
Hit Ok - Voila... it has turned all the values into negative numbers. I think the finance manager was pretty impressed that the solution flowed from me quite quickly. However full disclosure I had done a sneaky google... and used this as a guide.