Excell is a typo of Excel, and a word/name in it's own right
Excell gives 2630000 (2.6M) hits on Google (94M hits for Excel)
It's hard to tell the value, obvious a good name, but the extension could be
better. The owners of the other extensions might be interested in it.
If you were to sell it right now it could probably fetch mid-high XX,
to an end user maybe low-mid XXX, and "to the right buyer" possibly even more... :imho:
/Irkasmork