How to change Controls in gridview itemTemplate

Hi,
I have a problem I don't seem to figure out. How can I access controls (checkBox and label) inside dynamically generated gridview using IF inside  foreach loop? The idea is to check the database for time overlap, and if found to make label visible true and checkbox false.
I got it working up to the point of checking for time overlap and toggle the checkbox and label visibility. but it does not iterate through the individual rows. The outcome is either all labels are visible and checkbox not visible, or the other way around. What I need is to access the controls in the individual rows that time overlap it found in, and make label visible and checkbox not visible.  Is that possible?

Here is the code behind:
protected void CheckAvailability_Click(object sender, EventArgs e) { //take text from start date and start time, and convert the date to 'Date' and the time to 'Time ...