Need help with this transformation

*** Given input xml with uniqe (requestnumber & evidencenumber)
combinations

<Results>
   <Result>
      <RequestNumber>1</RequestNumber>
      <EvidenceNumber>1</EvidenceNumber>
      <Result>3.1</Result>
   </Result>
   <Result>
      <RequestNumber>1</RequestNumber>
      <EvidenceNumber>1</EvidenceNumber>
      <Result>3.2</Result>
   </Result>
   <Result>
      <RequestNumber>2</RequestNumber>
      <EvidenceNumber>1</EvidenceNumber>
      <Result>3.1</Result>
   </Result>
   <Result>
      <RequestNumber>2</RequestNumber>
      <EvidenceNumber>1</EvidenceNumber>
      <Result>3.1</Result>
   </Result>
</Results>

*** How would you recommend I get to the following

<Results>
   <Result>
      <RequestNumber>1</RequestNumber>
      <EvidenceNumber>1</EvidenceNumber>
      <Result1>3.1</Result1>
      <Result2>3.2</Result2>
      <Deviation>.1</Deviation>
   </Result>
   <Result>
      <RequestNumber>2</RequestNumber>
      <EvidenceNumber>1</EvidenceNumber>
      <Result1>3.1</Result1>
      <Result2>3.1</Result2>
      <Deviation>0</Deviation>
   </Result>
</Results>

*** I am still cuttin my teeth on thinking like XSL
(declaritive/functional) So I could use some help figuring out the
pattern to solve this problem of coallation and computation.
To be honest if I solve the coallation problem I think I will be 90%
there no?

Thanks

Sean