I put up a question to the R list on using VBA macros from within excel. It seems you can use R from within Excel and can customize it so that the end user doesnot know R. It is called RExcel (what else !)
Quoting Erich from R archives ”
There is RExcel (available by downloading the CRAN package RExcelInstaller. It allows to transfer data between R and Excel, and run R code from within Excel. So you can start with your data in Excel, let R do an analysis, and transfer the results back to Excel. You can write VBA macros which do this, but “hidden from exposure”,
so the Excel user does not even notice that R is doing the hard work.
It also has an Excel worksheet function RApply which allows to call an R function from an Excel cell formula. =RApply(”rfun”,A1)
would apply the R function rfun to the value in cell A1.
If the value in A1 changes, Excel will force R to recalculate the formula.
There is a (half hour long) video demo about RExcel
http://rcom.univie.ac.at/ has more information about the project
This can help save a huge number of costs as Excel is the least expensive analytical software and is present on all analytics companies.
More news on R here http://bits.blogs.nytimes.com/2009/01/08/r-you-ready-for-r/