using networkdays with blank cells

[sooroo]

I am trying to get some help regarding a report I'm trying to create. There are many columns of dates - basically tracking at what stage the different projects are at. Some projects only have a few dates filled in, and some have the majority filled in.

I'm trying to find the cycle times of each phase of the project, but sometimes there are empty cells because the phase/project has not been completed yet. I am trying to find a way to replace an empty cell with today's date so that I can figure out the current cycle time of the entire project, as well as each phase.

I thought that I could do a formula that tested if the cell is empty, and if the cell was empty, I could replace it with today's date. However, I have 2 problems - 1. I don't know how to test if a cell is empty when writing a formula. The only approach I could find was if(X2=" ") for non blank cells. 2. I am a novice to networkdays, so I don't know if this formula is being overtaxed.

One of my meager attempts was to try:
=IF(X2=" ","NA",NETWORKDAYS(X2,IF(Y2=" ",Y2,TODAY()),'Holiday Dates'!$A$1:$A$9))

X2=Date In
Y2=Date Out

Thanks to anyone for their insights

 

[sooroo]

Thanks all, I was able to get to the reference area. Hopefully this will be common sense in the future.