Hi I have a column with promised delivery dates. The Excel sheet I'm importing this data from has some blank values for this column which are coming in as null values which is messing up my calculation for delay in delivery (promised minus actual delivery date). I tried to replace the null values but they can only be replaced with date values which again will throw off my calculation for delay in delivery. Is there a way around this? I can't change the data type of the date column into text or anything else as I need to be able to perform calculations.