This is the solution that I used. Hope it can help everyone. 

Function SortListBoxArray(ByRef vTemp As Variant)
Dim vArr(), vSArr() As String, vItm As Variant, i As Long
vArr = vTemp.List
i = 0
For Each vItm In vArr
ReDim Preserve vSArr(i)
vSArr(i) = vItm
i = i + 1
Next vItm
SortStringArray vSArr
vTemp.List = vSArr
End Function
 
 
Sub SortStringArray(x)
' Function: sorts virtually any data type from smallest to largest
' Limitations: assumes entire array from LBound(X) to UBound(X) is to be sorted
' Passed Values: X [in, any] array of values
Dim i As Long
Dim J As Long
Dim temp
Dim PerDone As Double
For i = LBound(x) To UBound(x) - 1
For J = i + 1 To UBound(x)
If x(i) > x(J) Then
temp = x(i)
x(i) = x(J)
x(J) = temp
End If
Next J
Next i
End Sub
Thanks.