I will explain the way to calculate the value of the next month after selecting a month in a slicer and also within a range based on another date column:

I have those 2 tables:

Table1	Calendar

In the “calendar”, I will add this column:

• monthnum: YEAR([argument])*12+ROUNDUP(MONTH([argument]),0)

In the “table1”, I will add 3 columns:

• Opened month: using the “data groups”
• closemonnum: same formula as “monthnum”
• Closed month: using the “data groups” (optional)

I will create a relationship between “opened month” and “calendar”:

I will create 4 measures:

• To show the name of the next month:
  FORMAT(DATE(1,CONVERT(VALUES('table'[argument])+1,DATETIME),1),"MMMM")
  NOTE: to get the previous month, change “+1” by “-1”
  
• To calculate how many incident tickets I have for the next month:
  CALCULATE(CALCULATE(COUNT('table1'[argument]),ALL('table2'[argument1])),'table2'[argument2]=
  MAX('table2'[argument2])+1)
  
• To calculate how many incident tickets I have for the selected month based on the range of closed date:
  CALCULATE(COUNT('table1'[argument1]),FILTER('table1','table1'[argument2]=SELECTEDVALUE('table2'
  [argument])||'table1'[argument2]=SELECTEDVALUE('table2'[argument])+1))
  
• To calculate how many incident tickets I have for the next month based on the range of closed date:
  CALCULATE(CALCULATE(CALCULATE(COUNT('table1'[argument1]),ALL('table2'[argument1])),'table2'
  [argument2]=MAX('table2'[argument2])+1),'table1'[argument2]=MAX('table2'[argument2])+1||'table1'
  [argument2]=MAX('table2'[argument2])+2)
  

For my visuals, I will create a slicer using the “calendar” and when I select for instance “September 2024”:

• Measure: it is showing the next month name
• Measure 2: it is showing the number of incident for the next month
  
• Measure 3: it is showing the number of incidents for the selected month but only the ones closed on the selected month and the next month
  
• Measure 4: it is showing the number of incidents for the next month but only the ones closed on the next month and the next next month