function -hvad skal jeg skrive i min form for at udnytte dette

Jeg fatter ikke en brik. Hvad skal jeg skrive i min form for at kalde denne funktion?
Option Explicit
Option Compare Text

Public Function StjerneTegn(dato As Date) As Integer
Dim aar As String
aar = Format(dato, "yy")
Select Case dato
Case CDate("21-01-" & aar) To CDate("19-02-" & aar)
StjerneTegn = 1
Case CDate("20-02-" & aar) To CDate("20-03-" & aar)
StjerneTegn = 2
Case CDate("21-03-" & aar) To CDate("20-04-" & aar)
StjerneTegn = 3
Case CDate("21-04-" & aar) To CDate("21-05-" & aar)
StjerneTegn = 4
Case CDate("22-05-" & aar) To CDate("21-06-" & aar)
StjerneTegn = 5
Case CDate("22-06-" & aar) To CDate("22-07-" & aar)
StjerneTegn = 6
Case CDate("23-07-" & aar) To CDate("23-08-" & aar)
StjerneTegn = 7
Case CDate("24-08-" & aar) To CDate("23-09-" & aar)
StjerneTegn = 8
Case CDate("24-09-" & aar) To CDate("23-10-" & aar)
StjerneTegn = 9
Case CDate("24-10-" & aar) To CDate("23-11-" & aar)
StjerneTegn = 10
Case CDate("24-11-" & aar) To CDate("21-12-" & aar)
StjerneTegn = 11
Case Else
StjerneTegn = 12
End Select
End Function