Seems straight forward but I'm having issues - in short I purchased a security in '99 that reverse split 1:1000 then reverse split again 1:75 and was delisted in 2007 so I reported it is a worthless security to get it off the books this year (don't ask why it took so long). The rub is I only had 500 shares at the time of the split but even though each of the splits would have put me into fractions I still received 1 full share. Going through the calculations my basis is through the roof and doesn't seem right. Anybody have any suggstions on how to accurately determine my loss?

In summary:
bought 1000 share
sold 500 share
reverse split 1:1000 giving me 1 share
reverse split 1:75 giving me 1 share
delisted 1 share

Any help would be much appreciated