Hi Paul,
Yes it's possible to calculate within ATS. See an example below:
By using the action ‘Execute JavaScript Integer’ you can make calculations. For example: by entering the following script you can calculate using input parameters:
X = arguments[0] + arguments[1];
return X;
This will return the sum of the input parameters ‘arguments[0]’ and ‘arguments[1]’. The same works for “-“, “/” and “*”.
Hope this helps! On questions how the action works, please take a look at the online documentation: https://docs.mendix.com/ATS/refguide-ats-1/standard-actions-reference