Additional information is always helpful, especially a packaged dummy workbook with expected results.
I don't know how you define an Open contract but I assume you may have a field called [Contract Status]. From your explanation it appears you want to calculate the number of open contracts between 2 different date ranges. If that is yes then it means you already have 4 different date parameters (Start Date1 to End Date1 and Start Date2 to End Date2). Without any other information about your data structure, I'll suggest a generic solution below. You'd need to adjust it to match your dataset.
COUNTD(IF [Contract Date] >= [Start Date1] AND [Contract Date] <= [End Date1] AND [Contract Status] = 'Open' THEN [Contract ID] END)
COUNTD(IF [Contract Date] >= [Start Date2] AND [Contract Date] <= [End Date2] AND [Contract Status] = 'Open' THEN [Contract ID] END)
([Second Selection]-[First Selection])/[First Selection]
Hope this helps.
I really appreciate your response. It is helpful, but not quite what I am looking for. I will try to provide more context. My data source looks like the following:
Contract ID Name As of 1 Company 1 4/20/2018 2 Company 2 5/3/2018 3 Company 3 5/3/2018
If the contract is on the report it means it is open and needs to be closed. I have created some LOD calculations to tie the data into other sources that I have, including owners of the contracts. This has left me with the following on my Tableau sheet:
Ultimately, I would like to create a column that shows the % change of the number of contracts based on what dates are selected in the start date parameter and the end date parameter. For example, for the above, it would be a column that shows the % change between the numbers in the column under May 3, 2018 (what is selected for the end date) and the column under April 3, 2018 (what is selected for the start date). Therefore, the new column would be 10%, 0%, 0%, -3.8%, etc and would change depending on the dates that are selected.
It will be good if you can attach a dummy workbook. I can't be of much help without seeing some dummy data.
What field (dimension) do you have to the left of April 3, 2018 column? What is the measure being displayed in the table? Do you already have working parameters and all you need is just a column displaying % change of open contracts between Start parameter and End parameter?