Excel Array Formula

dear all

i really tried,ask , post my case in the message Board, but no solution yet .
a friend named(JeffReyBrown) suggested to post my case here.

in the attach, in Nigeria Sheet, i have in cell A1 a Drop down list for month , by chossing the month the date change in the range C5 to H44 base on an array formula

my need is to
1- make the formula smaller and faster.
2- Vba code that can do the work.

Appreciate any help and thanks in advance