Yes, calculations can be used in your repeating data forms. This is done in a similar way to the calculations used in study forms. 

If you don't want the study team members to see the output of the calculation field, you can set the calculations to be hidden. The output of the hidden calculations will be included in the export of your repeating data instances. 

You can also use the participant metadata, such as the participant ID and the site in your repeating data forms, if necessary. 

When using calculations in repeating data forms, please note that:

1. It is not possible to retrieve a field value from one repeating data instance into another repeating data instance.
2. It is possible to retrieve a study field value into a repeating data form field.
3. It is possible to retrieve a repeating data form value into a study field. This will be the field value of the repeating data instance that was created most recently.