SharePoint 2013 Make Calculated Column based on Custom Column

Question

In SharePoint 2013, I am trying to create a Calculated Column that is a shortened display of another Custom Column. The Calculated Column would just show the first 100 characters concatenated with "..." like in the following formula:

=LEFT([CustomColumn],100)&"..."

However, every time that I go to create this calculated column, SharePoint doesn't provide my [CustomColumn] in the "Insert Column:" list. If I type it in anyway, SharePoint throws an error.

Details on my Column, List, and Site below:

Col. Type: Multiple lines of text
Col. Group: Custom Columns
Col. Text Type: Enhanced rich text

List Content Type: Custom Type Inherits from Event

Site Type: Publishing

Also, to no avail, I found this similar post, but creating the Site Column and Calculated Column before adding it to the Content Type did not work for me.

Anyone out there know how to coax SharePoint into submission?!

Answer 1

According to this forum response from a Microsoft representative Multiple Lines of Text columns cannot be used in Calculated columns. The workaround that I always use for Calculated column limitations is to create a new field that will serve as your "fake" Calculated column (in your case probably a single line of text field) and then set the value using a workflow. If you do not want users to be able to manually edit the "fake" Calculated column then hide it from the new/edit forms using the SharePoint Manager 2013.

Note - This method is also useful for doing Calculated columns that use Lookup columns.