I am trying to run the following code in a spreadsheet

Heading = Application.WorksheetFunction.VLookup(Leftvalue, Num_Heading, 2, False)

The following error message comes up
Run - time error '1004'
Unable to get the VLookup property of the WorksheetFunction class.

I have tried it with different functions and it still comes up.

Running Excel 2000

Any ideas?