That's going to be extremely tough to determine. The MLS system for Bellevue is the NWMLS and I don't think it has complete info of sales data that far back. For instance, I just searched all single-family home sales between jan 1, 1998 and Dec 31, 1998 in bellevue and it only returned 5 houses. The only other way I can think of to get even close are these reports the NWMLS has.
For the area roughly bordered by: 405 to the west, I-90 to the south, 520 to the north and Lake Sammamish to the east (isn't exact, but close enough for now), the median sale price of single-family homes in January 1998 was just under $249K ...a whopping 46 units closed (that were listed with the NWMLS). In Feb '98, the median sales price was $220k, for march, $250k, april was $255k, may was $250k, etc. etc. ...it hits a high of $268k in August, and closes the year out at around $242k. This is just the entire area as a whole and really doesn't say much about your specific house.
I'm curious why you're trying to figure out what your house was worth nearly 10 years ago.