I've got this working nicely now thanks using this.
(Uses HttpUtils2)
B4X:
Sub Download (Callback As Object, link As String) As HttpJob
Dim j As HttpJob
j.Initialize("", Callback)
j.Download("http://mydomain.com/123.ABC")
Return j
End Sub
Sub Button_Download_Click
Wait For (Download(Me, "http://mydomain.com/123.ABC")) JobDone (j As HttpJob)
If j.Success Then
Log(j.GetString)
End If
j.Release
End Sub