Imports System

Public Module Module1

    Public Sub Main()

        Dim data As String = "M123456789^M123^C123^M1234^"

        Dim mIndex = data.IndexOf("M")

        Dim caretIndex = data.IndexOf("^", mIndex + 1)

        While mIndex > -1

            If (caretIndex > -1)

                Console.WriteLine(data.Substring(mIndex, caretIndex - mIndex + 1))

            Else 

                Console.WriteLine(data.Substring(mIndex))

            End If

            ' Search for the next match

            mIndex = data.IndexOf("M", caretIndex)

            caretIndex = data.IndexOf("^", mIndex + 1)

        End While

    End Sub

End Module