Multiple fonts in one Photoshop text layer?

I know how to create a text layer and set its contents and font


tell application "Adobe Photoshop CS3"
	activate
	set doc to make new document
	set textLayer to make new art layer of doc with properties {kind:text layer}
	set contents of text object of textLayer to "Hello, World!"
	set font of text object of textLayer to "GillSans"
	set size of text object of textLayer to 24
	set position of text object of textLayer to {4 as inches, 1 as inches}
	set justification of text object of textLayer to center
	set stroke color of text object of textLayer to {class:RGB color, red:255, green:0, blue:0}
end tell

How can I have part of the text layer be in a different font? For instance, in the example above, how would I make the word hello be in a bold version of a font?

To my knowledge there is no way to set the properties of text other than the whole layer. If you have Illustrator then you could script creating the text in that then place the .ai file as smart object. This can be done in CS2 with scriptlistener code an is a new feature of CS3 (I think) else you will have to create multi text layers.