Not Counting Blank cells in Checkbox formula

edited 12/09/19 in Smartsheet Basics

Hi All,

desperately need your help on this one. I've been searching the forums and tried this formula so many different ways and cannot get it to work. :(  

I have checkbox formula that is simple enough, I want it to check the box if we met the delivery date that was planned. So I'm comparing delivery date planned vs. Delivery date actual. This formula is working fine. IF([Delivery Date Actual]1 <= [Delivery Date Plan]1), 1, 0).

The problem is I do not want it to check the box if either of the cells is empty in either of these columns. I've tried using NOT(ISBLANK and the <>, "" formulas and it either changes all boxes to unchecked or doesn't work at all. :(

Any help is much appreciated!! Apologies if I'm overlooking something simple!