Please use this example to learn from. Please lookup each statement that you do not fully understand in the Help file.
Option Strict On
Option Explicit On
...
Dim intDelimiter As Integer
Dim strFull As String
Dim strSubString1 As String
Dim strSubString2 As String
strFull = "AL0120102090990AL01303030CS01999998888777"
intDelimiter = strFull.IndexOf("CS01")
If intDelimiter > 0 Then
strSubString1 = strFull.Substring(0, intDelimiter)
strSubString2 = strFull.Substring(intDelimiter)
MsgBox(strSubstring1 & vbNewLine & vbNewLine & strSubstring2)
End If
Note: Tested using Visual Basic 2012 (.NET Framework 4.0)