Is there a way (preferably in the template engine) to access the previous/next item in a DataList?

I have a Datalist, containing Worktimes, each Worktime is a has_one to a project (Project -> has_many(Worktimes))

I'd like to show in a template a list of worktimes.
If i Iterate through the worktimes

<% loop Worktimes %>$Project.Name - $Name<% end_loop %>

I get something like

MyProject1 - Something1 
MyProject1 - Something2 
MyProject2 - Something1 
MyProject2 - Something2

But I'd like to have something like

MyProject1 - Something1 
- Something2 
MyProject2 - Something1 
- Something2

So to speak, show the Project-Name only, if the previous Worktime is in a different Project...
My idea was something like this in the template:

<% loop Worktimes %> 
<% if Previous.Project.ID != $project.ID %> 
$Project.Name 
<% end_if %> 
$Name 
<% end_loop %>

For this to work the DataList Iterator would need something like a Previous/Next implementation. Any Ideas, how to achieve this?

Thanks,
MC

What you need is a GroupedList, so you could group your data by Project:

http://doc.silverstripe.org/framework/en/howto/grouping-dataobjectsets