Help Please.

I have a spreadsheet that has numbers in row 4 starting with column B and
extending to column DD. When the contents of row 4 for that column = S, I
then need to shade that column starting with row 5 through row 56 to the
color gray.

And if possible, when the above occurs insert the following letters in the
cells for that column in the rows as shown below.

An example is column G row 4 = S then

G10 value = P
G11 value = A
G12 value = Y
G13 value = S
G14 value = T
G15 value = O
G16 value = P

Thanks

Bill