MS Project Boolean Equation

I am drafting a two weekly lookahead programme that hopefully will be saved as a template for the use at a later date the problem i am faced with is i have two work shifts mainly day and night. i have decided to use the flag column to decide whether the work pattern is that of the day or night shift. i have further moved on to select a graphical indicator to help site staff see graphically when the activity is with relation to the shape of the moon icon. now for the hard bit, i cannot seem to get the formula to display another icon in this field. any help on the above matter greatly appreciated cheers