Coalesce

PART 2 of question I asked earilier.

What do I do with 'select  '<b>Subtotal:</b> ' + convert(varchar,(@Query1 - @Query2))'.  How do I use COALESCE when I need to subtract. If @query1 is zero then I should get a negative number


ALTER          PROCEDURE dbo.spGettotal
  @RptDate DateTime
AS

set nocount on

Declare @Query1 int
Declare @Query2 int
 
   Select @Query1 = Sum(Total)
     from (select distinct Total, billtype,unitid
             from tblBilling
            where convert(char(8), RptDate, 112) = @RptDate -1)as TMP

Select @Query2 = Sum(Totals)
     from (select distinct Batch, Totals
             from tblHospital
            where RptDate= @RptDate and Type LIKE '%KIP)as TMP

select 'Claims: '  + Cast(COALESCE(@Query1,0) As varchar(10)) as Totals
union
select 'Hospital Claims: ' + Cast(COALSCE(@Query2,0) As varchar(10)) as Totals
union
select  '<b>Subtotal:</b> ' + convert(varchar,(@Query1 - @Query2))