Extracting values from XML with jQuery

I am pulling the following response back from a page via jQuery ajax request.

I have been struggling trying to write a nifty function to extract specific values from the data given a set of criteria.

For example I would like to call a function and pass in 2 params, "TYPE" (i.e ANALOG, DIGITAL etc) and INDEX which specifies the index in that section.

So for example func("ANALOG", 8) would return 2.2 etc

I have tried to achieve this looping through a json response but with little sucess

 <response>
<ANALOG>
    <VARIABLE>
        <INDEX>7</INDEX>
        <VALUE>4.8</VALUE>
    </VARIABLE>
    <VARIABLE>
        <INDEX>8</INDEX>
        <VALUE>2.2</VALUE>
    </VARIABLE>
    <VARIABLE>
        <INDEX>9</INDEX>
        <VALUE>89.2</VALUE>
    </VARIABLE>
</ANALOG>
<DIGITAL>
    <VARIABLE>
        <INDEX>1</INDEX>
        <VALUE>1</VALUE>
    </VARIABLE>
    <VARIABLE>
        <INDEX>2</INDEX>
        <VALUE>1</VALUE>
    </VARIABLE>
    <VARIABLE>
        <INDEX>3</INDEX>
        <VALUE>0</VALUE>
    </VARIABLE>
</DIGITAL>
<INTEGER>
    <VARIABLE>
        <INDEX>2</INDEX>
        <VALUE>1</VALUE>
    </VARIABLE>
    <VARIABLE>
        <INDEX>3</INDEX>
        <VALUE>12</VALUE>
    </VARIABLE>
    <VARIABLE>
        <INDEX>4</INDEX>
        <VALUE>21</VALUE>
    </VARIABLE>
</INTEGER>

Any ideas welcome

Thanks