XML/XSL problem

Hi!
I am new in XML/XSL and I need help, plz!

I have this xml code:

<?xml version="1.0" ?>
<dataa>
<propo>
<client>Bambi</client>
<agence>Big Teddy</agence>
<proposition>badd</proposition>
<propositionM>baddGuy</propositionM>
<intervention>1</intervention>
<activite>z</activite>
<code>Mis1</code>
<price>475</price>
</propo>
<propo>
<client>Bambi</client>
<agence>Big Teddy</agence>
<proposition>badd</proposition>
<propositionM>baddGuy</propositionM>
<intervention>2</intervention>
<activite>x</activite>
<code>Mis2</code>
<price>205</price>
</propo>
<propo>
<client>Ana</client>
<agence>Little Marie</agence>
<proposition>good</proposition>
<propositionM>goodAfternoon</propositionM>
<intervention>1</intervention>
<activite>a</activite>
<code>Mis1</code>
<price>200</price>
</propo>
<propo>
<client>Ana</client>
<agence>Little Marie</agence>
<proposition>good</proposition>
<propositionM>goodAfternoon</propositionM>
<intervention>2</intervention>
<activite>a</activite>
<code>Mis2</code>
<price>250</price>
</propo>
<propo>
<client>Ana</client>
<agence>Little Marie</agence>
<proposition>good</proposition>
<propositionM>goodAfternoon</propositionM>
<intervention>3</intervention>
<activite>d</activite>
<code>Mis7</code>
<price>350</price>
</propo>
<propo>
<client>Ana</client>
<agence>Little Marie</agence>
<proposition>good</proposition>
<propositionM>goodAfternoon</propositionM>
<intervention>4</intervention>
<activite>d</activite>
<code>Mis2</code>
<price>50</price>
</propo>
<propo>
<client>Ana</client>
<agence>Little Marie</agence>
<proposition>good</proposition>
<propositionM>goodMorning</propositionM>
<intervention>1</intervention>
<activite>a</activite>
<code>Mis1</code>
<price>350</price>
</propo>
<propo>
<client>Ana</client>
<agence>Little Marie</agence>
<proposition>good</proposition>
<propositionM>goodMorning</propositionM>
<intervention>2</intervention>
<activite>b</activite>
<code>Mis2</code>
<price>400</price>
</propo>
<propo>
<client>Ana</client>
<agence>Little Marie</agence>
<proposition>good</proposition>
<propositionM>goodMorning</propositionM>
<intervention>3</intervention>
<activite>b</activite>
<code>Mis7</code>
<price>250</price>
</propo>
<propo>
<client>Ana</client>
<agence>Little Marie</agence>
<proposition>good</proposition>
<propositionM>goodMorning</propositionM>
<intervention>4</intervention>
<activite>e</activite>
<code>Mis1</code>
<price>550</price>
</propo>
<propo>
<client>Ana</client>
<agence>Little Marie</agence>
<proposition>good</proposition>
<propositionM>goodEvening</propositionM>
<intervention>1</intervention>
<activite>b</activite>
<code>Mis1</code>
<price>250</price>
</propo>
<propo>
<client>Ana</client>
<agence>Little Marie</agence>
<proposition>good</proposition>
<propositionM>goodMorning</propositionM>
<intervention>2</intervention>
<activite>a</activite>
<code>Mis2</code>
<price>500</price>
</propo>
</dataa>

I want to group "intervention" per "code" for "Ana" client and "good" proposition.
I want an html in which I'll have the information like this:
- mis1 activite price(for mis1)
- mis2....
- ....
- misn....... .
And I need the total sum of price in an html.
Could anybody help me with the indications for the corresponding XSLT ?