How to design windows service with timer of 1 minute ?

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C#

Windows

service

Hi I am designing the windows service in c#. I have set time interval of 1 minute.
How to check the previous process is completed on next timer start to prevent multiple entry.
I Want to check the previous service process if that process is not completed i want to skip this current process.

What I have tried:

i have set

public bool isComplete = true;

on timer i have checked

private void timer1_Elapsed(object sender, System.Timers.ElapsedEventArgs e)
{
    if (isComplete == true)
    {
        try
        {
            isComplete = false;
            eventLog1.WriteEntry("Service Initial Started at " + DateTime.Now.ToString() + Environment.NewLine);
            NexGenServiceRun();
            eventLog1.WriteEntry("Service Final Completed at " + DateTime.Now.ToString() + Environment.NewLine);
            isComplete = true;
        }
        catch
        {
            isComplete = true;
        }

    }
    else
    {
        eventLog1.WriteEntry("Service not started, Previous service is not completed " + Environment.NewLine );
    }
}