Code:

var

HTML_Doc: IHTMLDocument2;

Window: IHTMLWindow2;

oRange1: variant;

name_frame: OleVariant;

HTML_Doc := WebBrowser1.Document as IHTMLDocument2;

Window := HTML_Doc.parentWindow as IHTMLWindow2;

name_frame := 'mainFrame';

oRange1 := Window.frames.item(name_frame).document.body.createTextRange;