Matrix Style Reading: Reading from one cell to cause change in another cell

Hello Everyone,

I have created a sheet called 'Trials'. In it I have organized data in a matrix-style; the columns have a heading (A-O) and rows have a heading (1-54) in between cells are filled with banks and the word YES. Then I have made a dropdown box in cell F6 on a sheet called 'Main'. When the drop down is selected it shows a list of names of the headings from Columns B-P and shows values of A-O. This part is working fine (please see file attached). How do I make it so when a cell is selected from drop down in F6, it shows only corresponding heading, which is connected with the word YES to the row value. for example 1: If I choose from drop down box the value 'B', the values of choice in drop down box at G5(of Main) should be 22,23,24,25,26. If I choose from drop down box the value 'K', the values of choice in drop down box at G5(of Main) should be 18, 27, 31. Please see the attach file to get the visual understanding. Thank you so much in advance. Any help would be greatly appreciated.
regards,

SN

Thank you so much. I can work with this
cheers

If I wanted to add another word "Maybe" to match in some cells. and if the cell is 'maybe', it will appear in the dropdown list highlighted yellow.
I tried to modify the formula you gave to add "maybe" but it just shows blank:

=IFERROR(INDEX(A:A,AGGREGATE(15,6,ROW($A$2:$A$55)/(INDEX($B$2:$P$2,MATCH(Main!$F$6,Trial,0)):INDEX($B$55:$P$55,MATCH(Main!$F$6,Trial,0))=OR("Yes", "maybe")),ROWS(R$2:R2))),"")