.Xls files are Microsoft Excel files.
"Recordsets", as you're familiar with, are Microsoft ADO ActiveX objects.
Accessing MS Excel in MS Visual Basic on MS Windows ... sure (provided you have MS Office installed, of course ;-))
Accessing MS Excel, or doing COM/ActiveX, on Linux with KBasic ... good luck!
PS:
There's always OpenOffice and ODF format, which is completely open and completely portable to any platform/language you can imagine:
http://en.wikipedia.org/wiki/OpenOffice.org_Calc