It isn't clear what you are doing. Do you want to set up a new workbook
using code - this activity will be part of your application. Or are you
just creating a new workbook manually and want to know how to copy the
combobox and the code associated with the combobox.
You can copy a combobox by selecting it and doing edit=>copy, then select
the new sheet and do edit=>Paste
for code, you can go to the code, highlight it, and do Ctrl+C. Go to the
new module/location and click in the module, then do Ctrl+V
If it is more complex than that, then provide some details. For instance,
the Control Toolbox Toolbar has a combobox, as does the Forms toolbar and
you can get a dropdown in a cell with the list option of Data validation.
The first two can have code associated with them, but in each case, the
location of the code would be different.
So the more information you provide, the better people can provide
assistance.