Hope someone can help?

I have a form with combobox - if the user CHANGES the combobox (ie selects an entry where it was previously blank) and then saves the form, I want to send a signal from the combobox change procedure to my command button procedure to tell it what to do.

I have tried making the combobox change procedure public, but can seem to get the value to transfer to my private (Comm.button) sub.

I have not used public functions before, so not sure if this is the correct way to go about it.

Any help appreciated.
THanks