Checkedlistbox set checked items during initialisation

How can I check items before parent's form initialize ?

i do that in on_form_load events (AFTER checkedlistbox databind):

//Checked list default selection
for( int i=0 ; i < checkedListBox1.Items.Count; i++ )
{
checkedListBox1.SetItemChecked(i, true);
}

this code works fine if I launch it on checkedlist_double_click events.

Can u help me ?