thanks but that looked kinda complicated
However... I found this instead:
The Rotating Content Tool provides a simple way to add dynamic content to your web pages. You organize your content in advance and the content will then automatically rotate based on your criteria, either by specified dates or randomly. Learn more in the Overview or get started now creating your own content.
The Shared Content Library is a place where you can find ready-to-use content that others have created using this tool. You might even want to browse around the library to get an idea of how others are using the tool. (Once you create your own rotating content, consider making it available for others to use as well!)
It's really very cool and just what I wanted to achieve but wasnt able to write the code myself... although this is pretty simple now I have an example to work from