SetEnv ( var$, value$, overwrite )

Sets an environment variable named var$ to value$.
overwrite will determine if the call to this function should overwrite the variable if it exists

Example:
    SetEnv$ ("TEST_VAR","HELLO WORLD", 1 )

This example sets the TEST_VAR environment variable to the value "HELLO WORLD". It will overwrite TEST_VAR if it already exists.