Allow to password-protect a workbook, so that it cannot be shown (read) without the password.
Add support for preserving and exporting the macros in a macro-enabled workbook. Macros are pieces of code written in Visual Basic for Applications (VBA) which are used to automate repetitive tasks in excel. The macros are part of the excel file. When a file contains a macro its extension becomes xlsm. SpreadProcessing should be able to import and export xlsm files and edit the macros in them.
Implement support for cell references to columns and rows, e.g. $1:$2, A:D, etc. Currently, CellSelection.SetValue throws ParseException, and CellSelection.SetValueAsFormula throws InvalidOperationException.
Add support for Hidden and Empty Cells options:
With the current implementation, references like in the following expression cannot be evaluated and are treated as strings: =SUM('C:\Users\Your user name\Desktop\[Workbook_1.xlsx]Sheet1'!A1:B2)
Provide the ability to work with images in headers/footers of a worksheet. Note that large images put in headers are visualized as watermarks on printing/exporting to PDF.