Color Row Based On Fixed Cell & Relative Cells

My sales spreadsheets have a column which is turned to 100% when the order comes in (i.e. when the salesman gets it in his commission). I have applied conditional formatting to turn the whole row green when this happens (for ease of seeing which orders are in)

We also have a cell for the Purchase Order "number" (as these come from the customer, these can be a straight number sequence - "12345" or a mix of letters and numbers - "ABC12345"). My boss would like this cell to be red if the "order in" column is at 100%, but there is no PO number.

However, when I put in the formatting:
(1) =$K$15=1 (to turn the row green)
(2) Cell Value is equal to 0 (to turn the cell red)

it will apply (1) no problem, but will only apply (2) if (1) is false. (i.e. if (1) is true, the whole row goes green, with no red in the PO box.)

If I switch them round (i.e. have (2) first), then I get the formatting that I want (i.e. green row with a red box), but if (1) is false, I still get a red PO box.

What I need is a way of only applying (2) if (1) is true. (or any other way of only making the PO box red if the order is 100% but there is no PO number)