
DHTML Edit Control is an ActiveX control provided by Microsoft, they provide with it a sample app, this code is built on that app but much enhanced, to get the DHTML control goto:
https://msdn.microsoft.com/archive/default.asp?url=/archive/en-us/dnaredcom/html/cncpt.asp
also the project refrences WinMain's CodeMax control, if u don't have it, remove the refernce and replace it with a richtext box.....or whatever :-)