with .net call to excel range.merge()

[Guest]

I am trying to create and manipulate an Excel spreadsheet from a .net app and
trying to merge a range of cells. Intellisense gives the structure of the
call as follows:

void Range.Merge( object Across )

I am unclear as to what I need with Across Object . The Range object
already defines what cells are to be merged. if I pass something like this:

rng.Merge( rng );

I get an exception. Is there anywhere these calls are documented because a
search of google and Microsoft turn up nothing!!

Thanks,
Steve