How do I automatically change currency depending on another cell .
 

I am writting a worksheet that will be used on many projects. Each project
will have a copy of this worksheet and I will enter takings from each project
as they run. These projects will run in several countries and therefore the
takings will either be in pounds (sterling) or euros. I was wondering if it
is possible to create a drop down box or a check box that will give me the
option to change the currency that the sheet is using and for all other
currency cells in the sheet to react to that and change accordingly.