problem with a .fd file

[Jean Michel LECONTE]

I did a new function in a fd files 

fd_cumulative(l_fdv Start,l_fdv End,l_fdv U,l_int S,fdv A, fdv 
Sommedessizes)
{
      /* Interval Integrity  */
start Sommedessizes in 0..((trouvelemaxdelaliste(End) - 
trouvelemindelaliste(Start)) * max(A))
      /* resource histogram */
start resourcehisto(Start,End,U,S,max(A))
} 

I want to execute these two starts at each time the domain of a variable of 
Start, End, U and A changes
How to do ?? 

Thanks 


Jean Michel LECONTE 

i tried with trigger but i didn't find the solution