function Recalculate: TValueRec;
Re-evaluates expression in Context.
Returns: TValueRec - the result of expression stored in TMtxFunctionEvaluator.Context as TValueRec.
Remarks:
The procedure loads context from TMtxFunctionEvaluator.Context property, uses internal parser to evaluate expressions (now stored in TMtxFunctionEvaluator.Expressions property and returns result of expression evaluation.