QBASIC to check input character is capital or small using FUNCTION

DECLARE FUNCTION CHECK$(A$)

CLS

INPUT "Enter any character";A$

PRINT "The entered character is"; CHECK$(C$)

END

FUNCTION CHECK$(A$)

C = ASC(A$)

IF C > = 65 AND C < = 91 THEN

CHECK$="UPPER CASE"

ELSEIF C > = 97 AND C < = 122 THEN

CHECK$ ="LOWER CASE"

ELSE 

CHTR$="NOT A CHARACTER"

END IF

END FUNCTION