Add Second Function To Validation Formula

I'm trying to get a validation formula to work with Cell I2. It needs to check the number entered to make sure there is no dash, which is working with this formula:

=IF(ISNUMBER(SEARCH("-",I2)),FALSE, TRUE)

I'm trying to expand that formula to also check if there's a dash in Cell C2, and not allow the value to be entered in Cell I2 if there is a value without one.

So basically, it needs to make sure there is no dash in the value entered into Cell I2, and that if Cell C2 has a value, it includes a dash. (If there is no value in Cell C2, then no dash doesn't matter.)

How would I be able to make this work?