Indeed, as Jojo suggested, the arpeggio is limited.
One small tip for arpeggio's: you can exchange the last 2 digits. Example: C-4 J37 produces the arp in the following way: C-4, D#4, G-4, while C-4 J73 produces the arp in the following way: C-4, G-4, D#4
Although it doesn't exactly sound like a nice going up and down arp, it does get close to it.
Note that arpeggios only work with samples, not with VSTi's. If you're planning to use VSTi's, then its good to know that there are VSTi's out there (including free ones) that have a build-in arpeggio that can do what you want.
But for now, I would suggest setting the row speed to 3, tempo to 125 and pattern row-hilighting to: 3 rows per beat, 12 rows per measure. This'll give you great settings for a C64 kind of arpeggio. I used it in one of my songs to get a great C64 arp that I couldn't get otherwise (with a specific VSTi)
Here's a sample pattern for you to hear the result:
ModPlug Tracker MPT
|E-205......
|...........
|...........
|...........
|...........
|...........
|E-503v64...
|G-503v59...
|B-503v55...
|E-503v50...
|G-503v46...
|B-503v41...
|E-503v37...
|G-503v32...
|B-503v27...
|E-503v23...
|G-503v18...
|B-503v14...
|E-503v09...
|G-503v05...
|B-503v00...
|D-205......
|...........
|...........
|E-205......
|...........
|...........
|...........
|...........
|...........
|E-503v64...
|G-503v59...
|B-503v55...
|E-503v50...
|G-503v46...
|B-503v41...
|E-503v37...
|G-503v32...
|B-503v27...
|E-503v23...
|G-503v18...
|B-503v14...
|E-503v09...
|G-503v05...
|B-503v00...
|B-205......
|...........
|...........
Select the code, and copy paste it into your pattern using the above suggested settings.
Instrument 5 = bass
Instrument 3 = lead (arp)