This is the function to know the id
p_web.DivHeader('bCotizaciones_Cot:Ultimo_'&Cot:ID,'',net:crc,,loc:extra)
where bCotizaciones is the browse name, Cot:Ulitmo is the name of the column field and Cot:Id the Id of the row record
The result is like:
<div id="div690197848_div" >
Then, I know the id to modify via javascript