Formula column won't divide by 0

Formula column won't divide by 0

I have a simple formula column set up to calculate my cost per lead. It divides total leads by dollars spent. Frequently, I have instances where there are 0 leads with dollars spent. How can I make the formula column appear blank when this occurs? Right now it won't let me put 0 in, it populates "infinity" in the formula cell and won't let me save.