google sheets – How can I highlight a column of cells (H) if the date in the cell is more than a week old, and the cell next to it (I) is blank?

I’m trying to make a spread sheet to track open purchase orders. One PO per row. One column has the order date in it, and the next column has the receive date for the order. I’d like the cell with the order date to highlight red if the date in it is more than a week old, and there is nothing in the cell for the receive date. I’m new to this, so I scoured forums for a formula that would work, but it always says invalid formula. This is one I copy and pasted from a Q&A site:

=AND(TODAY()-7,(ISBLANK()C2:C))

It’s invalid, but I don’t know enough about this stuff to know why.