Direct conversion from PAGES (iWorks Pages) to XLSX (Microsoft Excel) is most likely not possible, because no dedicated pages to xlsx conversion exists.
However using the copy + paste method with both programs opened, it should be possible to copy certain elements out of opened .pages document and save it as .xlsx in Excel. That works only for Mac users, as there is no iWorks for Windows.
Unfortunately, there is no detailed software record in the database that match this conversion.
PAGES
pages file extension is used for default document format of Pages, a word processor and page layout program from Apple. No other program can open the .pages files, but Pages is able to export its documents to some other formats, such as PDF or Microsoft Word's .docx.
XLSX
Files with xlsx extension are s used by Microsoft Excel for its workbooks (spreadsheets) in Office Open XML format. XLSX is the latest spreadsheet format used by Excel with the adoption of XML formatting first used in Office 2007. While older xls files were in proprietary binary file format, xlsx spreadsheets use a somewhat altered XML scheme.