Small Bulk emailer with GUI

I want a bulk email program that will handle up to 100 recipients and have a simple graphic user interface to allow for the input of a date/time. This input should then be exported into one of three editable template email messages. At this time, I use a freeware bulk email program but have to copy and paste from a saved copy into a new message and change the times in each one. If I can simply enter the date/time in an input box and press send to accomplish this task it would make my life a little easier. There are only three messages in total. One informs of an impending event with the date and time that the event is expected. One informs of the actual start time of an event and the last one informs of the time that this event completed. All emails sent will be one of these three templates. The computer I will install this on is either WindowsXP or Vista. I have Outlook 2003 installed and currently use a Gmail account. This program will not be used for spam in any way. All recipients on the list will be there by request. If this is something that can be created for a reasonable amount, then I would like to proceed with this project. If the scope of this project far exceeds my budget then I apologize for my ignorance and certainly mean no insult.