when the page loads the piclist value should be same formula field .

i have to display the data from two different objects i consist of formula fiels and the picklist value  here i need keep the picklist value basedon the formula i differes for every record here mycode  can someone can help will be appericate more 
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   public List<SelectOption> getUnitOrders() {
        List<SelectOption> options = new List<SelectOption>();
              
       Schema.DescribeFieldResult fieldResult =  Catalog__c.Units__c.getDescribe();
       List<Schema.PicklistEntry> ple = fieldResult.getPicklistValues();
       
        for( Schema.PicklistEntry f : ple)
        {
          options.add(new SelectOption(f.getLabel(), f.getValue()));
        }      
      
        
        return options;
    }    
   
    // Constructor load the inventory Items to page based on the user profile
   
    Public PlaceNeworders(){
   
    theOrder =new Order__c();
    inventoryList = new List<wrapNewOrder> ();
   
      User lgdUsr=[select id,name ,Distributor__c,profileId from User where id=:UserInfo.getUserId()];
      string profileName=[Select Id,Name from Profile where Id=: lgdUsr.profileId].Name;
      inventoryList = new List<wrapNewOrder> ();
    
      if(profileName == 'System Administrator'){
    
             invItems = [SELECT Id,Cut_and_Size__c,Fresh_Frozen__c,Quantity_Available__c,Species__c,Price_per_Unit__c,Units__c FROM Inventory_Item__c where Quantity_Available__c > 0];
          }
      else{
             invItems = [SELECT Id,Cut_and_Size__c,Fresh_Frozen__c,Quantity_Available__c,Species__c,Price_per_Unit__c,Units__c FROM Inventory_Item__c where Distributor_Name__c =: lgdUsr.Distributor__c AND Quantity_Available__c > 0];
          }
     
      for(Inventory_Item__c a: invItems) {
                // As each Order is processed we create a new wrapAddOrder object and add it to the inventoryList
                inventoryList.add(new wrapNewOrder(a));
            }
            System.debug(' Print enter'+inventoryList);
   
   
    }


// Insert the order and order items

public PageReference confirmNewOrder() {


        if(theOrder.id==null){
            theOrder.Buyer__c = selectedRestaurantId;
            theOrder.Requested_Delivery_Date__c = datename ;
            insert theOrder;
           
            system.debug('TheOrder inserted'+theOrder);
        }
                         
         List<Order_Item__c> items = new List<Order_Item__c>();
         for(wrapNewOrder wno : inventoryList) {
         
          if(wno.selected==false){
                ApexPages.Message msg = new ApexPages.Message(ApexPages.Severity.FATAL,'Please select atleast one item');
                ApexPages.addMessage(msg);
            }
                   
            if(wno.selected == true) {
        
               Order_Item__c oItem = new Order_Item__c();
               oItem.Amount_Ordered__c = wno.amount;
               oItem.Comments__c = wno.splInstructions;
               oItem.Desired_Units__c = wno.selectDesiredUnit;
               system.debug('@@oItem.Desired_Units__c'+oItem.Desired_Units__c);
               oItem.Order__c = theOrder.Id;
               oItem.Inventory__c = wno.invItem.Id;
                items.add(oItem);
             
              System.debug('Print Amount'+wno.amount);
              System.debug('Print SpL'+wno.splInstructions);
              System.debug('Print id'+theOrder.Id);
            }
             
        }
       
        if(items.size()>0){
              insert items;
              System.debug(' -------item----------- '+ items);
              PageReference orderPage = new PageReference('/apex/'+'/OrderFulfillment2?sfdc.tabName=01rF0000000VOWh');
              orderPage.setRedirect(false);
              return orderPage;
      
       
    }
       return null;
    }

  public PageReference Cancel() {
     
     PageReference orderItemPage = new PageReference('/apex/'+'/OrderFulfillment2?sfdc.tabName=01rF0000000VOWh');
        orderItemPage.setRedirect(true);
        return orderItemPage;
    }

       // This is our wrapper/container class.
      
         public class wrapNewOrder {
         public Inventory_Item__c invItem {get; set;}
         public Boolean selected {get; set;}
         public String splInstructions { get; set; }
         public Decimal amount { get; set; }
         Public String selectDesiredUnit{get; set;}
       
       

        public wrapNewOrder(Inventory_Item__c a) {
            this.invItem = a;
            this.selected = false;
        }
    }

}