to create a parameter by a formula

[tcardia]

Is it posible to create a parameter by a formula for a system family element? 

I need to create a parameter that subtracts the diameter of a pipe of the same dimension, would that be possible?

thanks

[azad.Nanva]

what did you mean? by python , dynamo or other way?

In revit normal formula, no you can not.this is not the programing language.

[CorstenGroup]

You may have to explain it bit more. 

[Corsten.Au]

Hello

Am attaching how to create a parameter which can pick any existing parameter ( like Diameter )

and you can further use it. even to subtract from itself.

Let us know if that helps or you have some other issue. 

ScheduleCalculated ParametersReuse Parameter