Can anyone help me to check this function?

[zargus]

Actually I am trying to create a function that can identify a postcode from a 'string' of address. The function should be able to verify the 5 digits (the postcode) which are located next to each other. The function that I have cannot function properly. Here is the function:

========================================
Function getpostcode (value)

dim leng As Integer
dim pc As String

For
leng=1 To len (value)
pc=mid(value,leng,1)
End if

If Is Numeric (pc) Then
pc=mid(value, leng,2)
End If

...........................

If Is Numeric (pc) =5 Then
getpostcode=pc
leng=Len (value) + 1
End If

Next leng
End Function
=========================================


I really hope there's someone out there can help me to correct the function. Thanks for your attention