As with anything in Excel, if you want to add the functionality to your program (which uses Excel) you can simply record a Macro of the actions, then use the code that is provided.
Admittedly you should remove most of the code in situations like this, as many other options are set too.
I recorded macros, and here is the code you want:
VB Code:
[b][i]sheet_object[/i][/b].PageSetup.Orientation = xlLandscape
[b][i]sheet_object[/i][/b].PageSetup.PrintTitleRows = "$1:$7"
[b][i]sheet_object[/i][/b].PageSetup.PrintTitleColumns = "$A:$C"