Error establishing a relation in access database through sql statement

[A Ms]

Hi I Execute the following sql statement successfully for a Access Database.

CREATE TABLE Scores (
StudentCode Text(9) NOT NULL,
CourseCode Text(7) NOT NULL,
SemesterCode Text(3) NOT NULL,
Score Double
);

CREATE TABLE Courses (
CourseCode Text(7) NOT NULL,
CourseName Memo NOT NULL,
CourseTypeID Integer NOT NULL,
CourseCategoryID Integer NOT NULL
);

ALTER TABLE Scores ADD CONSTRAINT PK_Grades
PRIMARY KEY (StudentCode, CourseCode, SemesterCode);

ALTER TABLE Courses ADD CONSTRAINT PK_Courses
PRIMARY KEY (CourseCode);

ALTER TABLE Courses
ADD CONSTRAINT UQ_Courses_CourseCode UNIQUE (CourseCode);

But Finally I Get Error message(Syntax error in CONSTRAINT clause.) on this satement that is at the end of my execution list.

ALTER TABLE Scores ADD CONSTRAINT FK_Scores_Courses
FOREIGN KEY (CourseCode) REFERENCES Courses (CourseCode)
ON UPDATE CASCADE;

And I don't know Why? Please Help me on how to establish a relation in access database through sql statement?