Client side validation in footer row

[Roger Moore]

I have a timesheet application with a variable number of rows, depending on
how many projects the user is working on at the time. Each row has twelve
columns with a textbox in each, one for each day of the week, with only one
textbox for weekends. These textboxes are in the ItemTemplate, so they are
always in existence. (There is no Edit mode.) The footer has a textbox for
the days as well.

What I would like to do is have an onblur event for the ItemTemplate
textboxes run a JavaScript function that will update the textbox in it's
corresponding footer textbox. Is this possible inside a DataGrid? I am
having problems figuring out how to associate control ids when it is created
dynamically.

Thank you,
Roger