On what table is your layout based?
And what have you set up in Manage | Value lists?
What you describe is something I call a "hierarchical conditional value list" and it requires a different relationship structure to make it work. Each of the tables that hold data for one of the value lists in the hierarchy must indivdiually and directly link to the layout's table.
Pay especial attention to the last link in this list once you can get the first conditional value list working.
Forum Tutorial: Custom Value List?
Knowledgebase article: http://help.filemaker.com/app/answers/detail/a_id/5833/kw/conditional%20value%20list
Hierarchical Conditional Value lists: Conditional Value List Question
Feel free to post follow up questions here if those links aren't enough to get your value lists working correctly.
Thank you PhilModJunk, I will let you know how I go.
Thanks a million PhilModJunk
I resolved the issue by first changing the relationships to the Pole table as per image below, then changing the controls from a drop down list to a pop up menu and "include only the related values" using the pole table.
Once again Thank you
This can also be done with a drop down list if you prefer that format over pop up menus...