I tried it on my MS 9 but it did not worked. However, Multisim does support Orcad design files -- extension ".dsn" -- which might be a workaround if you or someone has Orcad (or a demo version), you can open the symbol in Orcad and place it in your schematic, then save it as a ".dsn" file, and then open it from MS. Then you would select the component and do a 'save to database' operation.
Symbol files supported in MS have a ".sym" extension. However, in the symbol editor you can import pictures, bitmaps, ".dxf", etc. But in none of these I was able to open the ".olb" file you got.
Nestor