The can think of of two ways:

select *

into #temp

from OpenRowSet(...)

where 1=2

select count(*)

from tempdb.sys.columns

where object_id = object_id('tempdb..#temp')

drop table #temp

and use sp_OA procedures to launching Scripting.FileSystemObject. Open the file, and read the first line. # columns = # of commas + 1.