EXCEL 2000 Ignores leading zeros.

Can someone please help me “force” Excel 2K to recognise leading zeros in the output of a calculation. I’ve tried every formatting trick I know,and can display these zeros, but not use them in further calculations: e.g. =left(), =MID(), =find() etc. Manually entered leading zeros are fine, but I’m almost frantic about the result when a formula is applied! With thanks, Raycpu.