There are a few methods to crack your issue wide open.
I am understanding that you are using a C-Shell (I use Bash, but certain environment I interact with use the TCSH.).
One method to accomplish your requirement is systemic process-oriented locking.
The Process Locking approach looks most like this:
set process_id = $1
set sub_sequent_cmd = $2
set ANTECEDENT_PROC = XXYYZZ
while (pidof $ANTECEDENT_PROC)
if (pidof $ANTECEDENT_PROC)
The premise of the solution is what's important. Monitor the proc with an external script, and when the antecedent proc ends, execute your subsequent script.
This would only work if you refactor your csh script to be invoked in an exported csh session.