the following will get a double from a hard coded byte-array but hopefully it should work with your data
Dim b() As Byte = {1, 2, 3, 4, 5, 6, 7, 8}
Dim ms As New IO.MemoryStream(b)
Dim sr As New IO.BinaryReader(ms)
Dim d As Double = sr.ReadDouble()
sr.Close()
ms.Close()
not sure if the answer is right but worth a try