Still can't get the code below to work ,  for some reason I don't have the reply button, only the Answer button and when I use that to respond it's marking my own responses as best answer even the question is not solved yet.
 

trigger LeastCompetitorPrice on Opportunity (before insert, before update) {
    Integer highestPricePosition;
    Decimal highestPrices;
    Decimal lowestPrice;
    for(Opportunity opp : Trigger.new){
        //Add all our prices in a list in order of competitor
        List<Decimal> competitorPrices = new List<Decimal>();
        competitorPrices.add(opp.Competitor_1_Price__c);
        competitorPrices.add(opp.Competitor_2_Price__c);
        competitorPrices.add(opp.Competitor_3_Price__c);
        
        //Add all our competitors in a list in order
        List<String> competitors = new List<String>();
        competitors.add(opp.Competitor_1__c);
        competitors.add(opp.Competitor_2__c);
        competitors.add(opp.Competitor_3__c);
        
        //Loop through all competitors to find the position of the highest price
                   
        for(integer i = 0; i<competitorPrices.size();i++){
           Decimal currentPrice = competitorPrices.get(i);
           if(highestPrices == null || currentPrice > highestPrices){
                  opp.HighestPrice__c = highestPrices;
			system.debug(highestPrices);
                     opp.HighestPrice__c = competitorPrices.get(highestPrices);
              if(lowestPrice == null || currentPrice > highestPrices)
                  highestPricePositions = i;
                             
           }
        }
         //Populate the leading highestPrice field with the highest price
         // matching the highest price position
        // opp.Leading_Competitor__c = competitors.get(highestPricePosition); 
        
        
        
    }}