I think I've explained it all here, but I might have left something out:

In Wkbk1, Wksht1, look at every row that has something in it. If the contents of the range cells Ax:Bx of the row don’t appear in Wkbk2, Wksht1, Ax:Bx, copy the whole row and paste it into the next empty row of Wkbk2, Wksht1.

Any help/hints appreciated.

Thanks
Rob