Know-How Exchange : E-Marketing

#Intro:
I work with several colleagues in- and outside the office. They all have their own products & services for which they do email-marketing. Unfortunately there is overlap between the audiences, so we use a Google doc excel sheet to map and plan which campaigns go out to whom. We have agreed to the conditions internally about the frequency that certain audiences are emailed for certain products of services.

#The problem:
- Not everyone is as careful with planning and double checking their audiences are already being approached at the same time.
- It is hard to have a clear overview in the sheet.
- For no particular reason some people can, and some people can't use the filter in Google doc.

#The question:
What kind of tool are you using to plan and agree on email campaigns across your company? I am not talking about the mailing system that can determine what a person receives and how often, but one step before that: the actual planning.

#Requirements:
- Accessible by multiple people at the same time
- Able to build in conditions, such as "If audience A is selected for Date X no-one else can select audience A for Date X to Z.".

THANKS