crontab. sqlplus cannot execute

please help me.
i made a script...
the script cannot work...
the error message appear is SQLPLUS cannot execute
i have already prepared the sqlplus at the proper path
but script cannot execute..."sqlplus cannot execute"...i try use
login root and usual user.still cannot work.
but when i run normal mode it work.
something problem when i use crontab with my script...help me
plizzzzzzzz...

Make sure your specify a full pathname, not a relative pathname.
Also ensure that any required environmental variables are set correctly.