Change user field value to value of another user field
Yes

Programmatically you have to create a custom form with submit button as the only field, now inside the submit handler it will be 2 step process something as below

following code I have written just to give an idea, and assuming field names in a way you can relate. You have to do the tweaks to make it work for you

/**
  * Form Builder
 */
function _my_module_reset_team_selection($form, &amp;$form_state) {
  $form = array();
  $form['reset_options'] = array(
    '#type' =&gt; 'select',
    '#title' =&gt; 'Reset Options'
    '#options' =&gt; array(
      'both' =&gt; 'Reset Both Teams',
      'ft'   =&gt; 'Reset Friday Team',
      'tt'   =&gt; 'Reset Tuesday Team',
    )
  );
  $form['submit'] = array(
    '#type' =&gt; 'submit',
    '#value' =&gt; 'Reset',
  );
}

/**
 * Submit Handler for your custom form.
 * 2 step process 1. Find Users to Update. 2. Update :)
 */
function _my_module_reset_team_selection_submit($form, $form_state) {

  // Logic to decide if to reset both or any one
  // possible values as 'both'/'ft'/'tt'
  $reset = $form_state['input']['reset_options'];
  // Step1. Get All the Users who are part of any team.
  $users_to_reset = _my_module_get_users_to_reset($reset);
  if (is_array($users_to_reset) &amp;&amp; count($reset)) {
    // Step2. Update to Reset.
    switch ($reset) {
      case 'both':
        foreach ($users_to_reset as $user_to_reset) {
          // For better performance you can use field_attach_api here**
          // I am using user_save() process
          $user = user_load($user_to_reset);
          $user-&gt;field_tuesday[$user-&gt;lang][0]['value'] = '';
          $user-&gt;field_friday[$user-&gt;lang][0]['value'] = '';
          user_save($user);
        }

        break;
      case 'ft':
        foreach ($users_to_reset as $user_to_reset) {
          // For better performance you can use field_attach_api here**
          // I am using user_save() process
          $user = user_load($user_to_reset);
          $user-&gt;field_friday[$user-&gt;lang][0]['value'] = '';
          user_save($user);
        }
        break;
      case 'tt':
        foreach ($users_to_reset as $user_to_reset) {
          // For better performance you can use field_attach_api here**
          // I am using user_save() process
          $user = user_load($user_to_reset);
          $user-&gt;field_tuesday[$user-&gt;lang][0]['value'] = '';
          user_save($user);
        }
        break;
    }
  }
}



/**
  *  Helper Function to get list of users to reset.
  *  Allows you to reset any of two Tuesday Team or Friday Team or both.
 */
function _my_module_get_users_to_reset($reset='both') {
  $get_tt_users = array();
  $get_ft_users = array();
  if($reset != 'ft') {
    $get_tt_users = db_select('field_tuesday_team','tt')
                 -&gt;fields('tt',array(entity_id))
                 -&gt;condition('tt.entity_type','user',"=")
                 -&gt;execute()
  }               -&gt;fetchCol();
  if($reset != 'tt') {
    $get_ft_users = db_select('field_friday_team','ft')
                 -&gt;fields('tt',array(entity_id))
                 -&gt;condition('tt.entity_type','user',"=")
                 -&gt;execute()
                 -&gt;fetchCol();
  }
  $users_to_reset = array_unique(array_merge($get_tt_users,$get_ft_users));
  return $users_to_reset;
}