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Dear D_G_D,
Good day! Thank you for posting to Microsoft Community. We are happy to help you.
As per your description, it seems that you are trying to calculate column based on the column in different SharePoint lists
If the understanding above is right, we're afraid that there's no out of box way to achieved this in SharePoint currently as the lookup column is not supported to use in calculated column for now. Sorry for the inconvenience caused.
For your reference: Calculated value for a list column - Microsoft Support
As far as we know, there's a possibility that this can be achieved via Power Automate flow as a workaround. considering that the community moderators here focus on out-of-the-box features in SharePoint, so we have limited experience customizing the Power Automate flow, we suggest you post your concern in the related **** Microsoft Power Automate Community for expert assistance. This is a specific support channel related with Power Automate where users can get the dedicated and professional support from experts and engineers there.
Similar request we've found in that community for your reference:
Solved: calculate the value of a lookup column (powerplatform.com)
Solved: Calculate a date based off a list (powerplatform.com)
Apologies for redirecting you to a different community as category members have limited knowledge about flow building, to make sure you can get the best and fastest assistance, we redirect you the right way.
Appreciate your patience and understanding and thank you for your time and cooperation.
Please let me know if I made any misunderstanding of your thread or there have anything else I can do for you. I hope you a great and nice day!
Sincerely,
Rhoda | Microsoft Community Moderator