I am trying to automate a call to a remote server using WinSCP which
Your syntax does not even remotely resemble WinSCP command-line syntax for scripting.
See WinSCP article on Checking file existence using scripting:
@echo off
set REMOTE_PATH=/home/user/test.txt
winscp.com /command ^
"open ftp://username:password@ftp.example.com/" ^
"stat %REMOTE_PATH%" ^
"exit"
if %ERRORLEVEL% neq 0 goto error
echo File %REMOTE_PATH% exists
rem Do something
exit /b 0
:error
echo Error or file %REMOTE_PATH% not exists
exit /b 1
The above example is for FTP protocol. You didn't tell use what protocol are you using. If not FTP, you have to change the open command accordingly.
You can have WinSCP GUI generate the open command for you.
Once you have the batch file ready, use Windows Scheduler to call it regularly.