Hi Jane,
I think you're speaking about Daniel 9, I didn't see the original post or others in response, but I'd thought I'd throw another opinion in the mix.

I think it is speaking about Messiah restarting the prophecy time line.  He will restart the last week of the 70 weeks.  It is the Lord who brings desolation concerning abominations.  An example:
Jer_44:2  Thus saith the LORD of hosts, the God of Israel; Ye have seen all the evil that I have brought upon Jerusalem, and upon all the cities of Judah; and, behold, this day they are a desolation, and no man dwelleth therein,

So, it will occur in the midst of the week.
Kari