VBA Function To Extract Number Groups From String And Separate Them With Hyphen?

I need a VBA function to extract number sequences from a string and separate them with hyphens In the example below cell A1 has the value 'xx2 yyy34 zz515' The code must produce the value '2-34-515' from the above example I have the following function that extracts the numbers but need a way to separate the groups with a hyphen

Code:
Function parseNum(strSearch As String) As String
Dim i As Integer, tempVal As String
For i = 1 To Len(strSearch)

[Code]....