If Statement in Excel

I am trying to create this formula in a column to do two functions. I have columns B and I set to be filled with dates. I also have column J set to calculate the number of days between those 2 dates. What I want to happen is if column I has a date, column J will stop counting days up, but if column I has no date it will keep counting up days. What I came up with as the formula for this is =IF(I2="",=TODAY()-(B2),(I2-B2)), but it doesn't seem to work. Any ideas?