Imports System.IO
Dim LogStream As FileStream 'should be at a level with enough scope for your logging

'Start the logging to your file - probably to go in your frmMain.load
LogStream = New FileStream(System.IO.Path.Combine(System.Environment.CurrentDirectory, "MYFILE.log"), FileMode.OpenOrCreate)

Dim objTraceListener As TextWriterTraceListener = New TextWriterTraceListener(LogStream)

Trace.Listeners.Add(objTraceListener)

'Whenever you want to log a message use the vb.net 
trace.writeline("message") 
'and it will get written to the log file.

'Close the log file when your application ends
If Not LogStream Is Nothing Then
Trace.Flush()
LogStream.Close()
End If