What´s wrong with this? I have "Firstname Lastname"

I want "Lastname" and "Firstname"


Function Manipulate_string(ByVal strName As String)


Dim str1() As String
Dim str2 As String
Dim str3() As String
Dim str4 As String
strName = Left(strName, Len(strName) - 1)

str1 = Split(strName, " ")
str2 = str1(1)

str3 = Split(str2, " ")
str4 = str3

'En msgbox för att visa hur slutresultatet blir

MsgBox (str4 + str2)
Manipulate_string = str4

End Function