Datetime---URGH! please help

I am currently trying to pull information of a SQL Server.
I have a [lastupdate] field which is in Datetime format.
Here is my code

Select * FROM DPRData Where Location = 'All PCGs' And lastupdate Like '%23:59:59' order by ID desc

Our system updates every hour and I need the last update which is at 23:59:59 every day for a whole month.

I have tried everything eg:

Select * FROM DPRData Where Location = 'All PCGs' And lastupdate Like '%23:59:59%' order by ID desc

Select * FROM DPRData Where Location = 'All PCGs' And lastupdate = '23:59:59' order by ID desc

This actually works and brings back the last entry for that day however bringing back every day....

Select * FROM DPRData Where Location = 'All PCGs' And lastupdate = '20041010 23:59:59' order by ID desc

I am pretty new to this and generally I can search on google and get my answers. However I am going to get in a lot of trouble at work if I don't find a solution so please help.

Caz

Hi Guys,
I am calling a method that manipulates the Database to come up with the date but when it comes back to the method its a string so I either need to cast the string to date or use date variable in the method either way i need to know the code of casting or using the date variable in the method to fetch the database for a date.

thanking you in advance for all your support.

Ayaz