jquery.between.js

// Source: http://www.ferretarmy.com/2010/05/10/extending-jquery-selectors-between/

$.expr[':'].between = function(
    objNode,
    intStackIndex,
    arrProperties,
    arrNodeStack)
{
    var args = arrProperties[3].split(",");
    var startSelector = args[0];
    var endSelector = args[1];

    var startIndex = -1;
    var endIndex = -1;

    // Find the start and end indexes.
    for (var index = 0; index < arrNodeStack.length; index++)
    {
        if ($(arrNodeStack[index]).is(startSelector) && startIndex < 0)
            startIndex = index;
        else if ($(arrNodeStack[index]).is(endSelector) && endIndex < 0)
            endIndex = index;
    }

    if (startIndex >= 0 &&
        endIndex > 0 &&
        intStackIndex > startIndex &&
        intStackIndex < endIndex)
        return true;
    else
        return false;
};