Although the advice to search on MSDN is a good one, sometimes MS does its best to obfuscate information. As a service to all, I rummaged about and managed to find the definition of the XlFileformat Enumeration (aka, the options you would use in scripting via VBA or Win32::OLE to save):

http://msdn.microsoft.com/en-us/library/bb241279.aspx

I think the one you want for xlsm is xlOpenXMLWorkbookMacroEnabled