insert a command button

Hi guys,

Here's my problem:
I want to insert a command button and assign a macro, I have the developers toolbar available with the controls section and on all other spreadsheets i can then select insert and choose the required button, however on the particular workbook i want to use the insert button is greyed out and not available.
i already use macros in this workbook and they work fine from keyboard shortcuts but i would like to make one of them run from a command button
Is there a simple setting somewhere which i may have turned off inadvertently previously or could the problem have anything to do with the macros themselves?

Thanks
Lee