In Ethan Frome what reason does Ethan give for not driving Zeena to the station?

Ethan, who is not very practiced at lying or deceiving
people, doesn't want to take his wife to the station, because he wants to be at home
where he can spend more time with Mattie during her absence.  Taking her down to the
station would ruin the chance he would have to spend at least one evening alone with
Mattie; if Jotham takes Zeena, that would leave Ethan the freedom to have time with her,
and no servant around to bother them.  So, he conjures up some story about how he has to
go into town and get money for the lumber.  Originally, Jotham was going to take the
lumber into town, but Ethan says that he wants to do it in order to get paid for
it.

Unfortunately, he is not going to get paid for the
lumber at all, and he knows that telling Zeena he will be will give her hope
that

"he was
in funds on the eve of one of her therapeutic
excursions."

This would
encourage her to buy expensive remedies that in reality, they couldn't afford.  But, his
desire to spend time alone with Mattie and to avoid Zeena overwhelms that caution, and
he sticks to the lie.  I hope that those thoughts helped; good
luck!