Hi Brittany,
There are a couple of different ways to achieve this depending on what your requirements are.
(1) You can create a new custom field on your project custom form that will work out the difference between the two dates so that you can then reference it in reports and visualise the data in graphs / charts. To achieve this you would simply add a calculated field to your project custom form and add the calculation: WEEKDAYDIFF(Planned Completion Date,Target Launch Date).
(2) You can add a column to an existing project report, switch it to text mode and add the following code. This will add a new column to your report view which will display the difference between the two dates. You wont be able to use this in graphs or charts and it will only work on the report where you have added this custom column
displayname=Date Difference
textmode=true
valueexpression=WEEKDAYDIFF({plannedCompletionDate},{DE:Target Launch Date})
valueformat=HTML
Hope this helps! Please shout if you have any questions.
Best Regards,
Rich.
