I am trying to create a function that uses the vlookup worksheet function to
look up a value from the previous sheet. eg. The sheet "Mar 2005" will lookup
the values in "Feb 2005" and then "Feb 2005 " will look at "Jan 2005", and so
on, the sheets are in order Jan 2005, Feb 2005,... . The function is only to
ask the user the value to look up and then it will look up the previous
corresponding table on previous sheet.