Ok your going to have to break up that cell, I'm sure there is a more complex code or formula that can do what I am going to suggest, but this will keep it simple (I hope

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Try the expression below in a query that is the control source of your report. Replace the field name [address] with your field name.
Expr1: Right(Trim([address]),Len(Trim([address]))-InStr(1,[address]," "))
*You can change the Expr1 and give it a more meaningful name.
I tried it out and it works provided there is a space after the street number in all the records (as normally would).
So I am assuming that the record source is a query, you paste the expression above, into the next blank cell of your query change the name [address] to match your field. This will give you a new field which will be available in the report.
You can then use this field to sort the report, it does not have to be visible.
I picked up the expression from the MS knowledge base:
http://support.microsoft.com/default.aspx?scid=KB;en-us;q115915
If your record source is NOT a query, then just make a new query using just the table bound to the report, and make the new query the record source.
Ziggy