Thanks Guys for your help.
So i used the SetActSymbol with another Resource and worked exactly as i expected it to what is great.
Still issues with Truss as Josh mentioned im guessing this is because its part of the truss insertion tool what is kinda annoying.
I made a few scripts for different types of resources like light fittings and also some for truss at different lengths. all the light fittings worked but when going through the scripts for the different lengths of truss it just selected the last used length of truss not the length in the script..