A bass slide, other than upright or fretless, is very difficult to emulate, as the slide is not continuous but half-stepped as your finger slides over the frets.
Maybe an S900 guru can chime in... is there a bass slide sample in the S900?
If not, if you have a pencil tool and a good eye, you could draw in a fret glide by drawing in the semi-stepped (it's not REALLY exactly a half-step in the real world) slide rather than a straight line pitch bend (MIDI has pitch bend with it's own dedicated command, not any specific control #). But you also need to increase the default pitch bend range for the MIDI part - it's usually just a whole tone, you need at least a 4th and maybe a 5th of bend range (usually a MIDI commandable parameter). Then draw a descending ziggurat type pitch bend line and you are in the ballpark.
You might even get clever, and save a good one or two as MIDI files by themselves... just the commands for pitch bend range change and pitchbend data. Then paste into any style or SMF that needs one...