VBA index

[Cobra17]

I can't seem to get this index to work in VBA

SP1Mxa = Application.WorksheetFunction.VLookup("a", "'[Library.xlam]Main Sheet'!" & SP1, Match("Mx", Index("'[Library.xlam]Main Sheet'!" & SP1, 1, 0), 0), 0)

the Index comes back with wrong number of arguments or invalid property assignment.

"a" is the row value I'm looking for
SP1 is the table name
'Mx" is the table header name i'm looking for

[davesexcel]

What should the formula look like without VBA?