steel quoting workbook

I am working on a spreadsheet to be able to quote different steel type, either by SF or LF. I have the SF figured out but I am having difficulty working with the LF sheet.

The tab named "LF TEMPLATE" is the one I'm working on now. It uses data from the "STRUCTURAL" worksheet for columns C, D and G. What I would like to be able to do is be able to select a material type in column C and have column D only display the available materials for that type. This would also only show the material weight in column G for the type and thk selected in columns C & D (I think this will work correctly as is). I'm stuck with how to get this to work. I've tried using data validation but no luck. Any help would be greatly appreciated as I'm not a great excel user and just try and pick things up as I go. thanks.