A family of Microsoft relational database management systems designed for ease of use.
...................but It does not list any fields in the nested subform.
Write the expression yourself. Subforms are not members of the Forms collection, so the syntax to reference a control in a subform is:
Forms![ParentFormName]![SubformControlName].Form![ControlName]
Consequently to reference a nested subform the syntax is:
Forms![ParentFormName]![SubformControlName].Form![NestedSubformControlName].Form![ControlName]
Note that SubformControlName and NestedSubformControlName are the names of the controls in the parent and first subform's Controls collections which house the subforms. The name might or might not be the same as its source form object.