Using and manipulating a variable in if statement in Power query

Hello, 

I wrote some code in the advanced editor, the goal of this code is to count the difference in days between the current record and the previous record in a certain group. I managed to do that by adding a column called 'Verschil in dagen'. So far, So good.

Now I have the difference in days in a column, I would like to group them within the current group and give them a unique ID.
The records are only allowed to be grouped if the difference in days between two records is smaller then 32, if it is not; a new group(read: id) should be created.

Since I am looping through the records already, I was thinking about creating a variable (Named 'TrajectCounter') that would simply count the amount of times the difference in days is smaller then 32. Here is where I get stuck.. 

TrajectCounter = 1,
#"Sorted Rows1" = Table.Buffer(Table.Sort(NewTable,{{"Factuur startdatum voorziening", Order.Descending}})),
#"Added Custom2" = Table.AddColumn(#"Sorted Rows1", "Traject_id", each   
                                   if [Verschil in dagen] < 32 or [Verschil in dagen] = null then 
                                      TrajectCounter 
                                   else 
                                      TrajectCounter + 1 )

The first part of the code runs fine and does what is has to do, when it reaches the else statement it's going wrong.
It should just + the 'TrajectCounter' variable by 1 and return it (and remember that is has been +'ed!).

I have tried something like this:

else 
   TrajectCounter = TrajectCounter + 1,
   TrajectCounter )

But that doesn't work.

Is there a way to plus the 'TrajectCounter' variable and return it in the same statement?