The objective function

Sub OPTIM_Objfunction()
 ' The function to optimise. 
 ' Note : The numerical quadrature ActiveX component INTG is called
 ' to evaluate the path integral
  Dim x(100)
  Dim obj_val, num_vars, a, b
  Dim result, numintervals, val, i

   num_vars = 3
   obj_val = OPTIM.Objval 
   OPTIM.getvars x(0), num_vars 
   numintervals = num_pts 
   a = 0.0
   b = 2.5      
   For i = 0 To num_vars - 1
      params(i) = x(i)
   Next           
   INTG.integrate a, b, numintervals 'evaluate the path integral
   val = INTG.answer ' assign the path integral to val
   obj_val = val
   OPTIM.Objval = obj_val ' make OPTIM_Objfunction return the value of the path integral
   OPTIM.setvars x(0), num_vars
End Sub