Dicom can evaluate expressions even with units. Unit conversion and
calculations can be carried out in 10 dimensions including currency. It
has built-in library of Scientific, Financial, Mathematical, and
various other functions. Can process rich text document with
calculations.
Free download available here:
http://www.knowbotron.com
More abou Dicom:
http://www.knowbotron.com/dicom/help/index.html