Classpath em execução

Programação Java
#1

Tenho um prog rodando e quero set o classpath para uma outra pasta.
Alguem tem ideia?

Process proc = Runtime.getRuntime().exec(“classpath=%classpath% ;D:\Temp”);

java.io.IOException: CreateProcess: classpath=%classpath% ;D:\Temp\ error=2
at java.lang.ProcessImpl.create(Native Method)
at java.lang.ProcessImpl.(Unknown Source)
at java.lang.ProcessImpl.start(Unknown Source)
at java.lang.ProcessBuilder.start(Unknown Source)
at java.lang.Runtime.exec(Unknown Source)
at java.lang.Runtime.exec(Unknown Source)
at java.lang.Runtime.exec(Unknown Source)
at test.TesteReflection.main(TesteReflection.java:20)

#2