Hi Aidy,
I see you are using Web View because for Web Generation the TPMonitor property should be INTERNET.
CSSCLASS is explicitly stated as not supported in Web View here: Windows GUI Specific Features - CA Gen - 8.6 - CA Technologies Documentation
I am not sure if CSSCLASS would work in Web Generation but you can try it if you are not locked into using Web View,
Also please note that the Toolset should not be used for Web View generation and only Gen Studio should be used (the availability of Web View generation option in Toolset is a hangover from when generation was needed from both Toolset & Gen Studio and the option has not yet been removed from the Toolset)
Generating Applications in Web View - CA Gen - 8.6 - CA Technologies Documentation
Other than that maybe using an HTML Control (javascript) can achieve what you need: HTML Mode - CA Gen - 8.6 - CA Technologies Documentation
Gen end users with more experience of Web client design might be able to provide more specific help.
Hope that helps.
Regards,
Lynn