function toggleSelectAll( source, formName )
{
    var form = document.getElementById( formName );
    if ( form == null )
        alert( "Unable to locate form: " + formName );

    // loop through all form elements, check if they are checkbox
    for ( i = 0; i < form.elements.length; i++ )
	    if ( form.elements[i].type == 'checkbox' )
            form.elements[i].checked = source.checked;
}

function deleteSelected( formName )
{
    var form = document.getElementById( formName );
    if ( form == null )
        alert( "Unable to locate form: " + formName );

    var itemCount = 0;

    // count all the items that are checked to be delete
    for( i = 0; i < form.elements.length; i++ )
        if ( form.elements[i].type == 'checkbox' )
            if ( form.elements[i].checked == true )
                itemCount++;

    // display confirmation messages
    if ( itemCount == 0 )
        alert( "U heeft geen items geselecteerd." );
    else
    {
        if ( itemCount == 1 ) message = "dit item";
        else                  message = "deze " + itemCount + " items";

        if ( confirm( "Weet u zeker dat u " + message + " wilt verwijderen?" ) )
            form.submit();
    }
}

/**
 * Add 'marked' class to the TR of the checkbox
 */
function toggleRowClass( elm )
{
    var trElm = elm.parentNode.parentNode;

    if ( elm.checked )
        trElm.className += " marked";
    else
        trElm.className = trElm.className.replace(new RegExp(" marked\\b"), "");
}