MOVE BACKWARD ALL IN my_cursor inside of function?

Is there a syntactically correct way to open a cursor inside of a user
defined function... and then use "MOVE" to move backward or forward
within it?

I keep trying something like:

 MOVE BACKWARD ALL IN _history;

but I keep getting a syntax error when I call the query, thusly:

ERROR:  syntax error at or near "$1" at character 23
QUERY:  MOVE BACKWARD ALL IN  $1

any suggestions are appreciated... not even sure if this allowed inside
a function.  note: i have no problems at all when I enter the examples
from the documentation interactively using psql--this error only occurs
for me inside my functions.

I hope there's a smarter/better way for me move back to the beginning of
my cursors without having to close/open them again...

thanks!

-marshall.