How to find the corresponding x-values from a graph

I have this data, which corresponds to x-values from 0->29.53 (in days) in intervals of 0.01 as shown on the excel spreadsheet attached, on the 1st Sheet. I have the graph plotted in the spreadsheet using scatter with lines of best fit.

Now from the same data, I need to find the Y-values for x values given in the 2nd sheet of the attachment that fit the graph. Does anyone know a simple way of doing this? The values appear to go up every 0.0035 or so but be waed they are inconsistent and skip a couple every so often.

Here's the link to the spreadsheet: https://drive.google.com/open?id=0B9sN4D6EYNaiblpxZFYtWldyYm8

Thanks in advance!