Hi,

Do the following formulae do what you want.
C3 and copied down
B3+2/24-IF(AND(F3<>"",B3-2/24>=F3-2/3/24),2/3/24,0)
D3 and copied down
=E3-2/24-IF(AND(F3<>"",E3-2/24>=F3-1/3/24),1/3/24,0)