It is good practice to open and close the VISA sessions. Assuming the data is actually going out the COM port as it is now, you are not looking for any data coming back. Is tehre responses to these message? Have you tried using HyperTerminal to determine these commands work? It is also bad practice to not wire your error clusters. If you did so, you would not need the sequence structure, and your code would be much easier to understand. You can also should have an indicator for the output error. Some people, such as myself do not have automatic error handling enabled, so I have no way of knowing whether an error has occurred without turning it back on.
You also seem to have carriage returns for some commands and not others. Do you know that the carriage return is the correct line termination caracter? It could be a linefeed or a carriage return and linefeed.
