Geting a data from others schemas

Question

Well I have the a problem I'm working in the schema Base and I need to know if an element exist in another schema , this schema is variable .
I have make this code , but is not ok
FUNCTION E_VEH (
BD VARCHAR2, V_VE NUMBER )
RETURN BOOLEAN
IS
NUMERO INTEGER;
V_SENTENCIA VARCHAR2(500);
BEGIN
V_SENTENCIA:=' SELECT COUNT() INTO NUMERO FROM :A.VEH
WHERE ID_VEH = :B' ;
EXECUTE IMMEDIATE V_SENTENCIA USING BD,V_VE;
RETURN (NUMERO > 0);
END;

Answer 1

Now I'm using the into stament but I'm getting the following error:
11:44:38 Target session: ORA-01006: la variable ligada no existe
This is my code :
FUNCTION EX_VEH (
BD VARCHAR2, D_VE NUMBER )
RETURN BOOLEAN
IS
NUMERO INTEGER;
V_SENTENCIA VARCHAR2(500);
BEGIN
V_SENTENCIA:=' SELECT COUNT(ID_VE) FROM :A.VEH WHERE ID_VEH = :B' ;
EXECUTE IMMEDIATE V_SENTENCIA INTO NUMERO USING BD,V_ID_VEH;
RETURN (NUMERO > 0);
END;