Macro to populate cell and then lock it

Hi All

I have a macro which works fine in Excel 2003. It's quite a simple one where I just populate a cell with a ZERO depending on what has been selected from a dropdown menu, and then lock the cell. Here's the code:

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However, when I open my file in Excel 2010, and try the macro, Excel just crashes.

Would anyone have any ideas as to why it crashes in Excel 2010, am I missing some code?

Thanks in advance
Simon

How about this instead:

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