I was just minding my own business when .... 用 中文 (繁體，臺灣) 要怎麼說？

I was just minding my own business=我那時候在弄我的東西UOyone door
eg. I was just minding my own business when you called me =你打給我的時候,我在弄我的東西(非常口語的用法)