Try this:

pgm = 'C:\ftp\des.exe '+ALLTRIM(FileName)
RUN &pgm

>Hi,
>
>I'm trying to use the RUN command using variables into the command line. The external program is a DOS encryption application and I'm trying to do this in VFP5. The result is bad command or file name. If I don't do the substitution it works fine. For example
>
>pgm = 'c:\ftp\des.exe' && this is taken from the .ini file
>filename = 'file.txt' && this is passed into this procedure
>
>RUN allt(pgm) + allt(filename)
>
>Any suggestions or solutions
>
>Thanks