Update command in vb.net,asp.net

[aplee]

hi Everyone,
My program is doing good when I suddenly bumped into this problem.
I dont know how to do the next functionality that I need to accomplish.
I am done with inserting values, showing the gridview etc and it works great. Now my problem is the update command.

I have 2 tables
table:tblDest
Fields:
destLastName
destFname
destEmail

Table:tblSource
Fields:
Sourcelastname
SourceFname
SourceEmail

Now, when I run my update command in sql server, it works great! I just right click the database, click new query and i run this command:

update tblDest set DestEmail =(Select SourceEmail from tblSource where tblSource.SourceFname = tblDest.DestFname and tblSource.SourceLastname = tblDest.DestLastname)

what the query does, is it updates the table tbldest email where lastname and firstname exists in both tables that are equal,
the question is, I want to automate this, I am done with inserting values, the problem is, I dont know how to run the update command,
I tried doing this:

Dim sqlds As New SqlDataSource
        sqlds.ConnectionString = ConfigurationManager.ConnectionStrings("sqlconnect").ConnectionString
        sqlds.ProviderName = ConfigurationManager.ConnectionStrings("sqlconnect").ProviderName
        sqlds.UpdateCommand = "update tblDest set DestEmail =(Select SourceEmail from tblSource where tblSource.SourceFname = tblDest.DestFname and tblSource.SourceLastname = tblDest.DestLastname)"
        DestGrid.DataSource = sqlds
        DestGrid.DataBind()

but nothing happened.

I want to thank you guys in advance for any help.