Hello,
the Rupee symbol is a relatively new character and may not be present in your current operating system. See this Wikipedia article for details
Quoting:
Unicode
On 10 August 2010, the Unicode Technical Committee accepted the proposed code position U+20B9 ₹ indian rupee sign (HTML: ₹ graphic:). The character has been encoded in the Unicode 6.0, and named distinctly from the existing character U+20A8 ₨ rupee sign (HTML: ₨), which will continue to be available as the generic rupee sign.
Ubuntu became the first operating system to support the Indian rupee symbol by default. Since its 10.10 version it has supported the symbol out of the box, as it was added to the Ubuntu font family by a contributor.
The rupee symbol has been added in Fedora 15, codenamed as Lovelock.
On 18 May 2011, Microsoft released an update to Windows Vista, Windows Server 2008, Windows 7 and Windows Server 2008 R2 operating systems to include support for this new Indian rupee symbol. This update includes font support, locale changes, and keyboard support. With the Windows update, it is now possible to use alt code text entry to obtain the Indian Rupee symbol - Alt 8377. (as of May 2012, testing this alt-code (Windows 7, MS Office 2010, and Canadian Multilingual Keyboard): it works fine in MS Word, MS OneNote, and MS Outlook. Does not work in MS Excel, nor does it work in Windows Notepad. It did not work for entry in a Facebook status update either. However, a workaround is that if you have the symbol in MS Word, you can copy the text character (highlight it and Ctrl C), then go to other application and paste it (Ctrl V), and the symbol appears exactly correct in each of these 3 mentioned applications.)
end quote.
In any case, you don't insert a symbol into a calculation, but you rather format the result of a calculation as a currency value. If the rupee symbol is not available in your operating system, you can resort to using the "Rs" convention by using a custom format, for example
"Rs "0.00;-"Rs "0.00";"Rs "0.00";@
cheers, teylyn