Is there a design pattern that abstracts a certain functionality from different applications [on hold]

Briefly,

We have many applications (1 .. n) with different functionalities, and they need to be interfaced by a dll that collects a certain parameters (most probably AppName, Values) and the dll will calculate a different formula based on the AppName/Values sent to it and then save these output calculated value to a file

The Requirements

• The scope of the dll is to calculate a formula for any application and record this output into a file

• The applications shall send only the name and a certain parmater to the dll that helps the dll to calculate a formaula

• The database has an associated formulas for each application

• The dll shall be flexiable to add and remove applications with the aid of the DB

• The application shall be abstracted from calculating the formula

• The paramters sent to the dll has to be unified for all the applications

• A new application shall register itself at the first time with the the number of paramters and a forumla

Is there already a design pattern, or can anyone define a way of how to design these requirements in an efficient way ?