What databases do you have access to?
If you are using LexisNexis for example, you could use a boolean search query in the case law field (e.g. "easement w/p gate and cost sharing arrang!").
If you are using BarNet Jade for example, you will generally need to type plain english in the search field (e.g. "easement and gate and cost sharing arrangement).
The problem with the plain English search is that you're likely to find hundreds of cases that aren't relevant to what it is that you are looking for exactly.
The problem with the boolean search is that you are likely to get very few if any results (because the search terms are so specific and there are other variables that you need to think about e.g. whether a different word to "cost sharing arrangement" would've been used in the judgement).
My gut reaction to your question is that you are looking for cases on on a very specific issue which might not exist.
What is it that you want to know? Do you want to know if the dominant tenement holder can erect a gate on the land subject to an access easement and demand a contribution from the servient tenement holder towards the cost of constructing that gate?
Maybe if you let us know what you're looking for, we can try to find a relevant case and then tell you how we would've searched for it (if any such case exists).
All the best.