Function/Formula To Determine If Workbook Open

how do you set a return value for a function in VBA? I've looked at examples of functions and I don't understand.

All I want to do is call a function to see if a workbook is open and have it return true or false. Here is the code I have, but it won't let me use go "Return isOpen" at the end like VB would! The IDE complains.

Function IsWorkBookOpen(ByVal name As String) As Boolean
Dim wBook As Workbook
Dim isOpen As Boolean

wBook = Workbooks(name)

If wBook Is Nothing Then
isOpen = False
Else
isOpen = True
End If

'I can't reutrn the value of is open?
Return isOpen

End Function

I've noticed other VBA functions I've looked at don't use "Return"....how does does the function return a value then?