Is there a way to make a hyperlink in Frame 12's CHM output open in a new brower window?

I am authoring in Frame 12 and using the Publish command to make HTML Help (CHM files).

To create hyperlinks, I format some text in FrameMaker with a character style, them add a Marker of type "Hypertext" to the text, using the marker text:

message URL http://www.address.com/" target="_blank

(sic! note the odd space after the first quote mark..... this syntax isn't documented by Adobe AFAIK, someone on these forums told me it in the past.)

This creates a hyperlink in the CHM that opens in a new Help viewer pane .... but really, what I want to do is open the link in a new browser pane (whatever the user's default web browser is).

Is there a syntax to do that?