Limit from 1 to 30 in an edit (xsl)

I have an edit in XSL and I just want to be able to write from 1 to 30 but I can not find how to do it.

I have tried with the min and the max but I see that you can not.

Any help?

Thanks in advance.

                    <widget size="45%,55%" bgvisible="false" >
                        <edit id="siguienteRonda" size="90%,20" class="editUpper" numeric="True" maxlength="2" label="{//PopShow/target/nextRound}"/>
                    </widget>