Can I override the actual tracing function?

Yes. You can do this by defining a custom WPP_TRACE macro. You must define your version of this macro before you include the trace message header (.tmh) file in the source file of your trace provider, such as a kernel-mode driver or user-mode application.

For an example of how to define a custom WPP_TRACE macro, see Can I preserve the last-error code before TraceMessage is called?.