I am trying to calculate some data, that i think sumproduct should do but i'm struggling with my fomula if anyone can help?

Data (sheet 1)

LTM | LTM | PYTM | PYTM | |

Customer No / Month | Aug-14 | Jul-14 | Jun-14 | May-14 |

1468 | 50 | 100 | 75 | 75 |

1206 | 200 | 30 | 125 | 100 |

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Summary - formula required (sheet 2)

Customer No | LTM | PYTM |

1468 | =Sum of Cust 1468 for LTM | =Sum of Cust 1468 for PYTM |

1206 | =Sum of Cust 1206 for LTM | =Sum of Cust 1206 for PYTM |

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I would really appreciate if someone could help.

Thank you!