how to use the expression tool in nx..

that means the inside toolbar in expressions.can anyone with image description pl.

3 Answers

See attached jpeg file, hope it helps

can you pl tell me full use why it has to be used

It is used when u want to define the parameters that can be changed according to expections. For example, u have the length of a pipe defined with L and u can change it just changing the parameter L from the expressions.
It has a wide range of use but this is what it is used basically.