Creating a Salesforce Trigger to Update Records

Creating a Salesforce trigger to update (in this case 'personnel') records involves writing Apex code to respond to specific events in Salesforce. Below is a basic outline of how you can create a trigger to update personnel records when certain criteria are met. In this example, we'll use a fictional object named `Personnel__c` and assume that you want to update a field on the `Personnel__c` object when related Opportunity records change.

Here's a step-by-step guide:

1. Log in to Salesforce:
   Make sure you have the necessary permissions and access to Salesforce setup.

2. Create a New Apex Trigger:
   - From Salesforce Setup, type "Apex Triggers" in the Quick Find box.
   - Click on "Apex Triggers."
   - Click the "New Trigger" button.
   - Choose the object you want to create the trigger for (e.g., `Opportunity`).
   - Name your trigger (e.g., `UpdatePersonnelRecordTrigger`).

3. Write the Trigger Code:
   In the trigger, you'll write Apex code that specifies when the trigger should fire and what it should do. 

Here's an example:

   ```apex
   trigger UpdatePersonnelRecordTrigger on Opportunity (after update) {
       // Create a set to store Personnel Record IDs to update
       Set<Id> personnelIdsToUpdate = new Set<Id>();
       
       // Iterate through the updated Opportunities
       for (Opportunity opp : Trigger.new) {
           if (opp.StageName == 'Closed Won') {
               // Add the related Personnel Record ID to the set
               personnelIdsToUpdate.add(opp.Personnel__c);
           }
       }
       
       // Query the Personnel Records to be updated
       List<Personnel__c> personnelToUpdate = [SELECT Id, FieldToUpdate__c FROM Personnel__c WHERE Id IN :personnelIdsToUpdate];
       
       // Update the Personnel Records
       for (Personnel__c personnel : personnelToUpdate) {
           personnel.FieldToUpdate__c = 'New Value'; // Update the field as needed
       }
       
       // Save the updated Personnel Records
       update personnelToUpdate;
   }
   ```

   In this code, we're updating the `Personnel__c` records when an `Opportunity` with the stage "Closed Won" is updated. Make sure to modify the criteria and field values according to your requirements.

4. Test and Deploy:
   - Before deploying, it's important to write unit tests to ensure the trigger works as expected.
   - Once your trigger is ready, deploy it to your Salesforce environment.

5. Activate the Trigger:
   - After deploying, make sure the trigger is active for the desired object (e.g., `Opportunity`).

This is a basic example of how to create a trigger to update personnel records in Salesforce. Please adapt the code to your specific requirements and ensure that you follow best practices for Salesforce development, including testing and proper deployment procedures.