Joining strings together, or concatentation, can take a toll on performance. Especially in a long loop. Here is a method to increase performance by 20x.
Sub Concat(Dest As String, Source As String)
'First Dest must have one space more
'Example : Dest = 'Hello '
'and not Dest = 'Hello'
Dim string1 As Long
Dim string2 As Long
string1 = Len(Dest)
string2 = Len(Source)
Dest = Dest & Space$(string2)
Mid$(Dest, string1, string2) = Source
End Sub