As you probably know, dynamic text fields allow to display automatically updated text information (drawing and object properties) inside DWG drawings. But some types of fields cannot be used inside blocks and xrefs - they are not updated there (their update cannot be influenced by FIELDEVAL).
Please note that there is no principal difference between a block (or an xref, external block) and a DWG drawing in AutoCAD - each DWG file can be xreffed or inserted into another drawing as a block.
So what is a contextual field? In addition to usual standard fields (with values like the current file name, author, etc.) there are also special contextual fields whose value varies depending on which space or layout they reside in. Each layout can have a different page setup attached, so the value displayed by the PlotOrientation field can be different in different layouts in the same drawing.
For compatibility with previous releases and fr logical reasons, such contextual fields in blocks and xrefs are not updated when you insert them in a drawing - instead, the field always displays its last saved value. If you wish to use a contextual field in a block (such as title block), do not insert the field as a text, but insert is a as a block attribute - attributes are updated. This field will then display (like all standard fields) its current value taken from the main, host drawing (from the drawing, in which the block is inserted).
For more advanced use of fields in multiple drawings you can use Sheet Set fields (also contextual).
- all sheet set fields
Note: In AutoCAD 2004 and earlier, all fields display their last saved value and are not updated