Excel date time formula

[avenkat]

I have 4 columns [TABLE="class: outer_border, width: 500"]
<tbody>[TR]
[TD]MAL[/TD]
[TD]MQL[/TD]
[TD]SAL[/TD]
[TD]SQL[/TD]
[TD]SQO[/TD]
[/TR]
[TR]
[TD]1/2/2018 1:20[/TD]
[TD]3/2/2018 3:30[/TD]
[TD][/TD]
[TD][/TD]
[TD]4/27/2018 4.30[/TD]
[/TR]
</tbody>[/TABLE]

I have a date that can be used as a reference to when a lead comes into this stage, I need to identify the gaps between the stages that will allow me to identify why a particular stage was not recorded.

Couple of things I need to do n have done
1) Find the day difference bet each stage - I used =DAYS(B2-A2) and so forth , but for the blank column I need to get a value that is blank and not a date value. What formula can give me a blank for eg D2-B2 = Blank

Also i need to get a value that will show increase decrease in no of days

 

[SpillerBD]

=if(or(a2=0,b2=0),"",days(b2,a2))

 

[avenkat]

Thank you for the help. What I really need is a formula that can give me which column does not have an entry int he progression .
For instance If data is missing in B/C then i need a formula that will help me extract that information.
For now I could only think of
If (A="",0,1) IF (B="0",1)....and finally do a SUMIFS(A:E )
but this does not allow me to isolate which column has a missing data.
Any pointers ?