I reformatted my earlier post. You should have been able to see my suggestion if you'd scrolled up? Here is the post again.
I suppose I'd either add a rule on Submit to set the HTML Coded string field, or I'd use a default value there. For a default value in the _HTMLCodedString field in your ior form:
xdMath:Eval(xdMath:Eval(../my:group1/my:group2, 'concat("", my:QTY, "", my:ItemNbr, "", my:UnitPrice,"")'), "..")