I think this is what you're referring to:
"This body comes into being through craving. And yet it is by relying on craving that craving is to be abandoned."http://www.accesstoinsight.org/tipitaka ... .than.html
There's also an instance where Ven. Ananda talks with a brahmin who says it's impossible to end desire with desire - Ven. Ananda asks if the brahmin still has the desire to come and meet him now that he's here already to clear that up.
I think there's also a passage where Ven. Dhammadinna says something along these lines (relying on craving to remove craving) to her lay-husband Visakha.