可不可以用be doing,when be doing?

可不可以用be doing,when be doing? 用be+doing +when be be doing sth.when 用be+doing 造句^-^ be+doing 用be doing when do造5句,是陈述句, 用when be doing/do/does句型造十个句子 用be doing when do造5句 如何对be doing sth when造句 各举一个be+doing+while+be+doing和be+doing+when+did的例句,be最好为过去时 用 be doing 和be doing to do 造句 三个 用be doing tomorrow造句