function aufrufen

wie kann ich aus einer function Z.b.:

Public Function SizeBMP(FilePath As String, Width As Long, _
Height As Long) As Boolean

Dim nFNr As Long
Dim nWidth As Long
Dim nHeight As Long
Dim nDummy As String

nFNr = FreeFile
Open FilePath For Binary Access Read As #nFNr
nDummy = Input$(18, nFNr)
If Left$(nDummy, 2) = "BM" Then
Get #nFNr, , nWidth
Get #nFNr, , nHeight
SizeBMP = True
End If
Close #nFNr
Width = nWidth
Height = nHeight
End Function

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Width
und Height herausholen?
ich kann die function ja nicht mit
y=SizeBMP(c:\x.bmp).Width
aufrufen, um an Width zu kommen