Android Question Wait For not waiting for job to finish

Sub PF_FileSize(sFileName As String) 
   
    Dim j As HttpJob
    Dim sPath As String
    Dim result As String=""
   
    sPath="http://xyz.in/App/Profile/" & sFileName
    If FileMap.IsInitialized=False Then
        FileMap.Initialize        
    End If
   
    j.Initialize("", Me)
    j.Head(sPath)
    Wait For (j) complete (j As HttpJob)
    If j.Success Then
        Dim length As List = j.Response.GetHeaders.GetDefault("content-length", Null)
        If length.IsInitialized  Then
            result=length.Get(0)
            FileMap.put(sFileName: Result)
        End If
    End If
End Sub