Isoview, is it possible to change the text value of a textbox via Javascript?

If I have a CGM with a textbox which has a text value of BLUE, can I use JavaScript to modify the value to say RED?

I was only able to find Iso3SetGrAttribute and Iso3SetStringAttrValue functions in Chapter 15 of the programmer's reference however it is not doing what I want it to do, or I'm using it incorrectly.