ID first and last non blank values in a row and return that cells column header

I have a data set with the weeks of the year as my column headers and a value of 1 (from a pivot table) in a distinct row value (removed for privacy) showing whether it existed in a given week based on pre defined criteria. What i need to do is ID the first (from the left) non blank cell in each row and then return that cells column header. I then need to do the same for the last (from the left) non blank cell in each row and then return that cells column header. On the attached I've put values in column N and O to show an example of what I need to return using a formula. Your help is greatly appreciated!
Mike
First instance.xlsx

I didn't download your file.

Try something like this:

Data Range

	B	C	D	E	F
1	Header1	Header2	Header3	Header4	Header5
2		x	x	x
3
4	1st	Header2
5	Last	Header4

This array formula** entered in C4:

=INDEX(B1:F1,MATCH(TRUE,B2:F2<>"",0))

** array formulas need to be entered using the key
combination of CTRL,SHIFT,ENTER (not just ENTER).
Hold down both the CTRL key and the SHIFT key
then hit ENTER.

This formula entered in C5:

=LOOKUP(2,1/(B2:F2<>""),B1:F1)

You're welcome. We appreciate the feedback!