About the UD User Defined Lookups Form
You can use the UD User Defined Lookups form to create custom lookups.
Lookups are windows that display when F4 is pressed in a field, showing valid data related to that field. Typically, lookups are assigned only to fields that require valid input from a specific table, such as Vendor (APVM), Job (JCJM), Phase (JCPM), and so forth. See F4 - Lookup for general information on lookups.
Once lookups have been created in this form, use the F3 window (Field Properties) to assign them to the associated field. Single or multiple lookups can be assigned to a field.