I think that you'd call it a variation of Henka waza, or changing from one technique to another
Henka means change or alternation. What you change is the form of the technique because your partner is resisting, or trying to counter or because there is another attacker (etc). In other words, the situation changes and so you change the technique.
If the change of situation leads you to another technique then I suppose you could say that it is henka waza, but more precise would be renraku waza (or renzoku waza).