risolto in questo modo:
codice:
<form name="frmCaf" method="GET" action="" enctype="multipart/form-data">
Data Agg.mento:<input type='text' name='txtDataAgg' onkeypress="if (event.keyCode==13) document.getElementById('idBottone').click();" value="" maxlength="11" size="6" class="INPUTInherit">
Nome:<input type='text' name='txtNome' onkeypress="if (event.keyCode==13) document.getElementById('idBottone').click();" value="" maxlength="5" size="4" class="INPUTInherit">
<input type="hidden" id="idBottone" value="Cliccami" onclick="subRicercaInCAF();">
<input type="button" onClick="subRicercaInCAF();" style="position:absolute;top:-20px;left:780px;color:#006699;width:100px;background:inherit;" name="cerca" value="Cerca in CAF">
</form>
ok...vi ringrazio.buona giornata