adjusting code add message quantity for inventory on userform

i have this code from mr. sintek so i would add message when i fill quantity if the quantity on userform > what existed in the sheet then show me message for instance code AA i fill 400q but it shows " this brand available only 346q " and if the quantity on userform < what existed in the sheet then show me message for instance fill code AA=10 but the real quantity=0 it shows this " this brand not available at all is 0 q"

HTML Code: