Generate arbitrary log entry/event?

I have developed a web form which relies on an application ID to perform iControl functions - for example, to disable a pool member. I have configured the audit log so that a log entry is generated when the object's state is modified using the form, but the log entry references the application ID which executes the iControl.

 

 

I have a way to obtain the real user ID with the web form, which I would also like to log. Is there some way to generate a log an arbitrary string or event?