Find string in textstream

[wmbb]

I'm using the folowing code

''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''
'' References:
'' MS DAO 3.6
'' MS Scripting Runtime
''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''
Sub ReadTxtImport()
On Error GoTo Err_ReadTxtImport

Dim fs As FileSystemObject, fd As Folder, fc As Files, f As File, ts As TextStream '' Variables for FileSystemObject
'Dim rst As DAO.Recordset
Dim strFolder As String, strFile As String
Dim strLine As String, strLineReturn As String
Dim strMagnification As String, strHighTension As String

strFolder = "C:\TextFiles\"

Set fs = CreateObject("Scripting.FileSystemObject")
Set fd = fs.GetFolder(strFolder)
Set fc = fd.Files

    For Each f In fc

        Set ts = f.OpenAsTextStream(1, -2)
        'Set rst = CurrentDb.OpenRecordset("tblTextFiles")
        
            Do While ts.AtEndOfStream <> True
                strFile = f.Name
                strLine = ts.ReadLine
                strLineReturn = Mid(strLine, InStr(strLine, "=") + 1)

                        If .....
                        End If
                

           Loop
    Next


ts.Close
rst.Close

Set rst = Nothing
Set ts = Nothing
Set fc = Nothing
Set fd = Nothing
Set fs = Nothing

Exit Sub

End Sub

I want a to look if the string "system on" is present in the textstream ts.
Subsequently the variable "answer" has to be set to "Yes" or "No"

Is this possible with a find funktion or does someone have a better idee.