how can I sum this function

This function is prediction for erosion of cavitation. I am writing udf for fluent. To this point udf is working.
How can I sum C_UDMI? I want to sum C_UDMI (erosion) for all time steps of calculation. Now it only gives me result of the last time step/iteration.

Here is current udf:

Code:

/********************************************************************
   UDF for calculating something and printing it to     
   console window at the end of the current iteration or time step  
*********************************************************************/

#include "udf.h"

/*************************************************************************************************************/
/*definiramo novo spremenljivko C_UDMI(c,t,0), ki se zapise le ob koncu casovnega koraka in je enaka C_STRAIN_RATE_MAG(c,t);*/
/*ne pozabi it v define-user defined-memory in dat prosto mesto!!!*/

DEFINE_EXECUTE_AT_END(execute_at_end)
{

  Domain *d;
  Thread *t;
  cell_t c;
  face_t f;
  d = Get_Domain(1);   /* mixture domain if multiphase */



thread_loop_c (t,d)

{
if (FLUID_THREAD_P(t))
       {

begin_c_loop(c,t)
  {
if (8.97*pow(1.1,2)*sqrt(C_P(c,t)/0.5542) > 118.745878036397)
    C_UDMI(c,t,0) = 26.7*pow(10,-5)/1484*(8.97*pow(1.1,2)*sqrt(C_P(c,t)/0.5542)-sqrt((200000000/998.2)*(1-(pow((1+200/300),-1/7)))));
else if (8.97*pow(1.1,2)*sqrt(C_P(c,t)/0.5542) <= 118.745878036397)
    C_UDMI(c,t,0) = 0.;
  }
end_c_loop(c,t)

}
}

}

Thank you for helping
Gašper