Is it possible to pick next row's cell value on same column if condition not matched?

I have a table flaggedcomment and a table price.

In flaggedcomment, there are two empty columns Price_DateTime and Price_Open which I want to copy from price, depending on the ON conditions. Query as below.

UPDATE flaggedcomment as t1 
        LEFT JOIN price as t2 
             ON t1.Ticker_Ticker_ID = t2.Ticker_Ticker_ID AND t1.Comment_DateTime = t2.Price_DateTime
SET t1.Price_DateTime = t2.Price_DateTime, t1.Price_Open = t2.Price_Open

This query will leave some cells with null value because there's no match between t1.Comment_DateTime and t2.Price_DateTime.

Is there a way to "pick" the next available Price_DateTime if there's no match found?

For example, if the value of t1.Comment_DateTime is 2014-09-29 20:44:00 but it's not exist in t2.Price_DateTime, can I pick the next row's Price_DateTime value, e.g. 2014-09-30 08:00:00?

I am new to deal with MySQL queries and I've tried my best in explaining what I want to do. If I didn't explain my question well, please let me know and I will try to explain it further.

Any help would be much appreciated. Thank you!