Fetching previous entry if particular date value doesn't exist

I want to Fetch Value for the last entry if entry doesn't exist on that date.

For Example:-

Currently what is happening, if i change date to previous and the record doesn't exist is shows me today's or the record which is displayed already. But I want to show last entered record in case the record does not exist.

Another Example..

DATE     |   GOAL
17       |   320 
16       |   420
13       |   300 

If user is pressing previous button and he is on 16 then user should get 13 date value on 15, As no Value exist for 15.