Do nothing in an excel formula

I want to write an “if” statement that if the value is false I want excel to do nothing, (not a 0 or anything). I want it to leave the data in the cell that is already there. Ex:

Formula in cell a6
=if(a2=”April”,b5+b6+b7,do nothing)

That way if I change the month to May I can enter the formula in c6:
=if(a2=”May”,b5+b6+b7,do nothing)
and it will keep the data in a6

I hope I explained this okay. Any help would be greatly appreciated!!!