[CentOS] Using shell variables inside the ftp client

I have a script that opens an ftp connection to a non-*nix system.
I desire to change directories on the host system using a shell
variable to set the cd directory. However, I cannot seem to
discover how this is done.

I have tried this:

TARGET=ftp-pickup

ftp
. . .

cd $TARGET

This gives the following error:

550 Failed to change directory.

I am using shell variables (put $TEMP_TXFR_FILE $OUTPUT_FILE)
elsewhere in this ftp session as arguments to get and put statements
and I have no problems. Is there some reason why I cannot use shell
variables as arguments to the cd command?

I am aware the $ is used to invoke .netrc macros but I have none
defined. In fact I was somewhat surprised, albeit pleasantly, when
the ftp client accepted shell variables as arguments in the get and
put statements.

Is there a way to dynamically define the target of a cd command
inside an ftp session?