as the need arises

Even so, he can be serious when the need arises.

The need for the college arose as a result of a change in the Government's education policy.

How else could you take care of her should the need arise?

And they can make do in no time, if the need arises.

As the need arose we would be told what to do.

Now, when the need for change arises, we are not in the position to do so.

She'd seen how quickly he could move, if the need arose.

Therefore, she has the ability to help her family when the needs arise.

Thus, the need arose for a club outside the university.

He could call upon that later, if the need arose.