”with half an eye”的中文是什麼？可否用中文成語作解釋？

英語 idiom 中有 keep an eye on something，意思係留意住一樣o野，要小心。
如果你o個句係 with half an eye on something，就類似 keep an eye on something，但冇咁留神，即係眼尾瞄住o個樣o野。如：
Ann's mother watched TV with half an eye on Ann, who had to finish her homework for next week.
但如果你o個句係 see with half an eye，咁就係用半隻眼都睇到，意謂一樣o野好明顯。如：
I can see with half an eye this is a fake Rolex watch! Why would anyone buy something like this?

句子的意思是：
一瞄便知

ok!!我諗到la!!!!!!


with half an eye嘅意思係「一半眼睛」。