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(User u ..)
Concatenates the contents of one or more user type fields into a user list field type. A "user" is an individual with whom you've shared your application. You'd translate something like an e-mail address into a user value so that QuickBase recognizes the user. When you do so, you can take advantage of user fields to design permissions and/or views. For example, show a user only those tasks that have been assigned to her.
Note: This field is of type List-User and therefore exercises the limit of 10 entries. If the resulting value of this field in a record exceeds the maximum entries allowed the resulting value will be set to blank.
ToUserList([Sales Manager], [Business Manager]) takes the values in the Sales Manager field and Business Manager field and returns the combined value into another field.