Return value based on 2 other cells

Hi all, please find attachment enclosed

In cells B16, B18, B20 and B22 I want the dates to display by formula.

I want to find the first blank cell (non f) which is coloured green for each product (lines 4,6,8,10) where there is a date populated in row 1.

As you can see in line 4, the first blank (green) cell is H4 - but there is no date in row 1. The first blank (green) cell with a date in row 1 is AV4 - so in cell B16 it displayed 23/02/2018.
Same for other 3 rows.

Can someone help with a formula to do this automatically?

=INDEX($1:$1,SMALL(IF(($C$1:$ZZ$1>0)*($C4:$ZZ4=""),COLUMN($C$1:$ZZ$1)),COLUMNS($A:A))) as array formula
unmerge cells
input formulas
merge cells

Thanks all for your replies. The non array formula is preferred in this instance but all good suggestions