How to call Functions

Private Declare Function SetCurrentDirectoryA _
        Lib "kernel32" (ByVal lpPathName As String) As Long

Public Function GetOpenFilenameFrom(Optional sDirDefault As String) As Variant
'Author       : Ken Puls ([URL="http://www.excelguru.ca"]www.excelguru.ca[/URL])
'Macro Purpose: To ask for a file at a specified directory
    Dim sDirCurrent As String
    Dim lError As Long
    'Make note of the current directory
    sDirCurrent = CurDir
    If sDirDefault = vbNullString Then
        'If optional arguement not supplied then
        'assign current directory as default
        sDirDefault = CurDir
    Else
        'If option arguement is supplied, test path to ensure
        'that it exists.  If not, assign current directory
        If Len(Dir(sDirDefault, vbDirectory)) = 0 Then
            sDirDefault = sDirCurrent
        End If
    End If
    'Change the drive and directory
    '*Drive change is unecessary if same, but takes as long to test
    ' as just changing it
    If Not Left(sDirDefault, 2) = "\\" Then
        'Not a network drive, so use ChDir
        ChDrive Left(sDirDefault, 1)
        ChDir (sDirDefault)
    Else
        'Network drive, so use API
        lError = SetCurrentDirectoryA(sDirDefault)
        If lError = 0 Then _
            MsgBox "Sorry, I encountered an error accessing the network file path"
        ChDir (sDirDefault)
    End If
    'Get the file's name & path, setting the filters to only display
    'desired types.  Help on the exact syntax can be found by looking
    'up the GetOpenFilename method in the VBA help files
    GetOpenFilenameFrom = Application.GetOpenFilename _
            ("Excel Files (*.xl*), *.xl*,All Files (*.*),*.*")
    'Change the drive and directory back
    If Not Left(sDirCurrent, 2) = "\\" Then
        'Not a network drive, so use ChDrive
        ChDrive Left(sDirCurrent, 1)
        ChDir (sDirCurrent)
    Else
        'Network drive, so use API
        lError = SetCurrentDirectoryA(sDirCurrent)
        If lError = 0 Then _
            MsgBox "Sorry, I encountered an error resetting the network file path"
        ChDir (sDirCurrent)
    End If
End Function

Public Function FileFolderExists(strFullPath As String) As Boolean
'Author       : Ken Puls ([URL="http://www.excelguru.ca"]www.excelguru.ca[/URL])
'Macro Purpose: Check if a file or folder exists
    On Error GoTo EarlyExit
    If Not Dir(strFullPath, vbDirectory) = vbNullString Then FileFolderExists = True
    
EarlyExit:
    On Error GoTo 0
End Function

Private Sub GetMeAFile_Click() 
.......
end sub

Private Sub GetMeAFile()'.....................................not possible
.....
end sub