Reading sections of a stdout output and doing UI operations based on the output

Question

I have a WPF application in which I am starting a process of Powershell from a different thread and redirecting the entire output to a textbox in the WPF window. The output of the window looks something like this:

STARTED PRODUCT 1 INSTALLATION
/* some lines here
   more lines 
*/
PRODUCT 1 INSTALLATION COMPLETE

What I want to do is that if, in between the STARTED and COMPLETE sections of text, any line or text containing "error" is spotted, I would like to update a particular icon and make it visible. Something like this:

if (text.Contains("error")
   Product1RedCross.Visibility = Visibility.Visible;
else
   Product1GreenTick.Visibility = Visibility.Visible;

This is showing kind of like a status by means of a red or green icon. If no error is spotted then it should display the green icon, showing that everything was fine.

My problem is that I have a bunch of different "Products". I would like to maybe take out chunks of text between "Started Product 1 installation" and "Product 1 installation complete" and check out if there is an error in there.

Otherwise, if an error is spotted, I won't be able to know for which product is the error being shown.

How can I achieve this and make it so that I can effectively determine where the error is and update the UI elements of that product accordingly.

My code for starting the process looks like this:

PowershellProcess.OutputDataReceived += new DataReceivedEventHandler((sender, e) =>
{
    if (!string.IsNullOrEmpty(e.Data))
    {
        StringBuilderOutput.AppendLine(e.Data);
        lock (this._myLockToken)
        {
            Dispatcher.BeginInvoke(
            new ThreadStart(() => OutputTextBlock.Text = StringBuilderOutput.ToString()));
            if (e.Data.Contains("PRODUCT 1 INSTALLATION STARTED"))
            {
                
            }
        }
    }
});

But here, I'm having trouble how I can work with sections of each product so that I can do UI operations without mixing other products up.