Read InternalCalcField to find out if the field represents a value provided by the underlying database but is not a field in the physical database table. Internally calculated fields are calculated by SQL servers or the Borland Database Engine in a live query view and stored in the dataset like data fields. 

For example, in the following SQL statement, the dataset includes a field for the calculated value ONHAND * COST.  

SELECT PartNo, Description, OnHand, Cost, (OnHand * Cost)
FROM PARTS

When the TQuery object has its RequestLive property set to true, the field definition for that calculated value will have InternalCalcField set to true.  

InternalCalcField is a read-only property. 

RequestLive 

FieldKind 

Using Internally Calculated Fields in Client Datasets