Your wrong Rwa, because Yogi_Bear_79 exit function after the first txtDir(i)="". The code look like this
Code:
Public Function MultiDirExport(ExportPath) 

Dim DirExport As String 
Dim I as integer
dim MaxI as integer
Maxi=frmMultiDir.txtDir.Count

For i=0 to MaxI
 If frmMultiDir.txtDir(0).Text = "" Then 
    Exit Function 
    Else 
    DirExport = frmMultiDir.txtDir(0).Text 
    DosShell "dir /b " & DirExport & " >> C:\Windows\Temp\MP3_Export.txt" 
 End If 
Next

End Function