The Requirements module links to the Releases module. The Releases module has an Incoming Links attribute that lists all the requirements that are connected to each release. The Requirements module contains an Implementation Cost attribute. You can use the LinkListAttributeSum business rule to calculate the total implementation cost for each release by summing the implementation cost of the requirements.
The following image shows an example of the Requirements module, which is the source module.
=LinkListAttributeSum("Related requirements", "Implementation Cost", "listen_to=Implementation Cost",'Related requirements')