Hi MS,
1. Yes, you r doing it correct. Just frist refresh the input form, #Ref disappear, enter the comment and then click save data.
2. If there is no comment you will see blank column after refreshing, so to make sure that the cell has funciton you have to add "if" function along with the EPMSaveComment formula, for e.g., if(EPMSaveComment(....) = "","No Comment",EPMSaveComment(....))
Hope this helps.
Regards,
Kalyan.