试试这个，免费控件。
CalcExpress is an interpreter for quick and easy evaluation of
mathematical expressions. It is a smart tool easy in use.
Supports 5 operators, parenthesis, 18 mathematical functions
and user-defined variables
Target Enviroment:
Delphi 4,5,6,7; C++ Builder 4,5,6; Kylix 2.0
Software type:
Freeware with source code
Company information
http://www.aidaim.com
works with real numbers;
accepts operators: + - * / ^;
accepts functions: cos, sin, tg, ctg, abs, sgn or sign, sqrt, ln,
exp, arcsin, arccos, arctg or arctan, arcctg,
sh or sinh, ch or cosh, th or tanh,
cth or coth, heaviside;
supports unlimited number of user defined variables
