Lookup across multiple sheets

[Bearded Dan]

I am looking for a way to look across multiple sheets for a given value and when found return the date in the same row as that value. In the sample file I have uploaded, on the Schedule page, the Date Sent formula needs to check all previous months for the R.O. number in column A and, if found, return that R.O.'s date in column M. I also need to transfer any comments in the same manner.