Formula Help - It's got me stumped!

Hi everyone, Looking for a formula which I'm sure is possible but it's got me stumped. I have a table that I'm wanting to add a formula to that brings back the date in the table header based on the last populated cell. I have added a picture as an example. The example would be for "Text 1" row, based on the last cell being populated by 40% I would like it to return the end date of 31-08-19 (hope this is making sense). For "Text 7" row, based on the last cell being populated by 100% I would like it to return the end date of 30-04-19. Any help would be great. Thank you :-) Paula