"Suppose when" 这个短语在英语中并不常见，但我们可以根据"suppose"这个词的用法来构造相关的句子。

Suppose作为动词，表示认为、推断、料想。例如：

I suppose you are right.

Suppose作为连词，引导条件状语从句，意为“假若”、“如果”。例如：

Suppose you have a thousand dollars, what will you do with it？

Suppose we go for a swim.

Suppose也可以用于表示建议或提出某种假定。例如：

Let us suppose another planet with conditions similar to those on the earth.

Suppose还可以用于表达不确定性或猜测。例如：

I don't know if he will come, but I suppose he will.

根据这些用法，我们可以构造一些包含 "suppose" 的句子：

Suppose作为动词，表示认为：

Suppose you are coming to China next year, what would you like to do？

Suppose作为连词，引导条件状语从句：

Suppose it rains tomorrow, what should we do？

Suppose用于表示建议：

Suppose we change our plans, what other options do we have？

Suppose用于表达不确定性：

I suppose she is still angry with me, but I'm not sure.

希望这些例句能帮助你更好地理解 "suppose" 的用法。