Financial dimensions Mandatory

How to write Code for financial dimension mandatory.

 [ExtensionOf(classStr(ProjJournalCheckPost))]

       internal final class DAXJournal_Extension

       {

           protected void postJournal(JournalTransList _journalTransList)

           {

               DimensionAttribute                  dimAttr;

               DimensionAttributeValue             dimAttrValue;

               DimensionAttributeValueSetItem      dimAttrValueSetItem;

               ProjJournalTrans                    ProjJournalTrans;

               RefRecId                            defaultDimension;

               JournalTransMap                     journalTransMap;

               boolean                             ret;

               next  postJournal(_journalTransList);

               journalTransMap = _journalTransList.item();

               projJournalTrans = journalTransMap;

               dimAttr             =   DimensionAttribute::findByName('Department');

               select firstonly RecId, DisplayValue from dimAttrValueSetItem

            where dimAttrValueSetItem.DimensionAttributeValueSet == ProjJournalTrans.DefaultDimension

         join dimAttrValue

     where dimAttrValue.RecId == dimAttrValueSetItem.DimensionAttributeValue

                   &&  dimAttrValue.DimensionAttribute == dimAttr.RecId

                     &&  dimAttrValue.IsDeleted == false;

               if (!dimAttrValueSetItem.DisplayValue)

               {

                   Warning("Department must be specified.");

               }

           }

       }