Project Plan / Timeline - lookup date by searching 'x' marker

Hi all, I am building an MS Project plan and decided to start from an Excel template so I can send it to each resource to complete themselves. I have formatted the sheet so wherever you place an 'x' the cell is coloured.

I now want to map the start date of the task and end date of the task by searching the row for the first 'x' and looking up to the date at the top. I also want to find the last x in the row and look up the date to give the finish date of the task.

Can someone please help me? I have tried variations of find, search and hlookup but don't know how to find the first or last 'x' in a row and then show the date. I tried an IF function too but it became unworkable.

Very good thank you! Took a minute to figure out but it works very well. I shall try and copy the structure for column b. Thanks for your swift response.