Natively, no. Notepad++ is a text editor, not a spreadsheet. Open your text file in Excel or OpenOffice/LibreOffice Calc or some other spreadsheet application, do the math, and save it again.

If you are willing to use a scripting plugin for Notepad++, it can be done, with more work. The Mathematical Replacement FAQ has all the details you need if you are willing to put in the effort yourself.