I continue without understand what you need exactly.

Anyway, to obtain the number of miliseconds from a datetime value, you can use something like this:

declare @Date DATETIME

SET @Date = convert(datetime, '2009-09-01 09:30:15.927')

SELECT convert(BIGINT, @Date)* 86400000

SELECT DATEPART(hh, @Date) * 3600000

SELECT DATEPART(mi, @Date) * 60000

SELECT DATEPART(ss, @Date) * 1000

SELECT DATEPART(ms, @Date)

SELECT (convert(BIGINT, @Date)* 86400000 ) + (DATEPART(hh, @Date) * 3600000) + (DATEPART(mi, @Date) * 60000) + (DATEPART(ss, @Date) * 1000) + DATEPART(ms, @Date)

And, the final result is:

Datetime: 2009-09-01 09:30:15.925

Number of milisenconds: 3460786215927

I hope this can help you.