[expert] PATH statement

[R_Yeo]

Hi,
        I am running tcsh and my path statement goes as follows:

setenv PATH "/bin:/sbin:/usr/local:/usr/local/bin:/usr/X11R6/bin:/usr/bin:"

I would like to add some more paths; how to I go about it?  When I just
add it into the same line and do a "source", it doesn't become active. 
What's the syntax I should use?  Something along the line:

setenv $PATH;blah

Again TIA

 -- Ronald