Load event gets executed many times why??

I was trying to fill a value in a text box in Packing screen on its page load .I used the following code

if (((pVal.FormType == 60017 & pVal.EventType== SAPbouiCOM.BoEventTypes.et_FORM_DATA_LOAD) & (pVal.Before_Action == true)))

{

SapApp.MessageBox("Event Started", 1, "ok", "", "");

oForm = SapApp.Forms.GetForm("60017", 1);

//some code

}

But the alert box gets displayed a multiple number of times.Why is it so?? Is there any better way to handle a form on load or is the event (.et_FORM_DATA_LOAD) i have specified here is wrong??