How to calculate the Percent change in a dynamic

Question

hi All,
I'm trying to get the percent increase/change of two dynamic
colums.  In my report, the user has a checkbox where he can select two colums to calculate the percent growth.
My DataSet is PilarName, Calification(is a decimal value) and Period (this is a string).  I created the Matrix this way:
PilarName [Period]
[PilarName] [Calification]
Which give me these values:
So, now I need to create another column to calculate the percentage change between these two colums.  I tried this:
I added a Adjacent column group for Period column and I grouped by the calculated column "ColumnDiff".  Add the following expression.
=(SUM(Fields!Calificacion.Value)- Previous(SUM(Fields!Calificacion.Value),"ColumnDiff"))/Previous(SUM(Fields!Calificacion.Value),"ColumnDiff")
After that I get: 
I'm getting the sum of the two columns instead.
Any clue about what I'm doing wrong? Please help me, I've been looking for the answer but any solution works for me.
Luis Carlos

Answer 1

Hi Luis,
According to your description, you have a report with different dynamic columns. Now what you want is show your user percentage growth in your matrix report after your user select two of those columns (I think you may use parameter to achieve your “checkbox”
function). Is my understanding correct?
In Reporting Service, we can’t calculate dynamic columns with our build-in arrogation functions. So we need to add custom code into our report, and call those functions which defined in custom code in our expression. We have tested your scenario in our local
environment. Here are steps and screenshots for your reference.
Go to your Report Properties, add the custom code below into your report:
Dim Shared Num1 As Double
Dim shared Num2 As Double
Public Function GetCalification(Calification as Double,Type as String,Type2 as String) 
If Type = Type2 Then
   Num1=Calification
Else
   Num2=Calification
End If 
Return Calification 
End Function
Public Function GetPec()
Return (Num2-Num1)/Num1
End function
Create a matrix. Put PilarName into Row field, put Period into Column field. In Data field, put the expression below into the textbox:
=Code.GetCalification(Fields!Calification.Value,Fields!Period.Value,Parameters!Period.Value(0))
In our sample report, we created a parameter (named Period) for selecting two columns. You can replace “Parameters!Period.Value(0)” with your own parameter.
Add an outside column at right (%Growth), put the expression below into the textbox:
=Code.GetPec()
Save and preview. The matrix and result looks like below:
Reference:
Custom Code and Assembly References in Expressions in Report Designer (SSRS)
If you have any question, please feel free to ask.
Best Regards,
Simon Hou