How to use goal seek function in Excel user function

Question

The following code demonstrates how to utilize goal seek in Microsoft Excel. It runs smoothly.

   Sub GSeek() 
      With Worksheets("Sheet1") 
             .Range("H18").GoalSeek _  
              Goal:=.Range("H21").Value, _ 
               ChangingCell:=.Range("G18")
     End With 
   End Sub

And I would like to use a function to do the goal seek like follows.

  Function fSeek(a As Range, b As Range, c As Range)
     a.GoalSeek Goal:=b.Value, ChangingCell:=c
     fSeek = "Ok"
   End Function

The code, however, operated without incident, and the range c received no response. Where have I gone wrong?

Answer 1

In the Microsoft Excel Object-Sheet1(Sheet1), we can only write the following code:

 '----------------------------------------------
 ' Goal seeking when the worksheet changes.
 '----------------------------------------------
 ' Here we want to do goal seek for Range("H18") 
 '  with the Goal cell as  Range("H21") 
 '  and  the changing cell as Range("G18").
 '
 Private Sub Worksheet_Change(ByVal Target As Range)
     Range("H18").GoalSeek Goal:=Range("H21"), ChangingCell:=Range("G18")
 End Sub