if statment in SQL SERVER strored procedure

the first part of code I working perfectly but the second part doesn't work at all and show error Incorrect syntax near 'EXEC'. Expecting CONVERSATION.

I tried to use select instead for set and also tried to use conversion function but this goes to fail

    if (@totalCash is null)
        BEGIN
          select @totalCash = 0
        END
    ELSE
        BEGIN
          set @totalCash = @totalCash
        END
    END




    declare @execute as int

------------------------------ قائمه التتدفقات النقديه EXEC @execute = CashFlowInsert 'التدفقات النقديه من أنشطه التشغيل' ,' ' -- التدفقات النقديه من أنشطه التشغيل --عجز (فائض ) إيرادات العام
-- > first Part declare @TotRevnu as int declare @TotExpens as int declare @totalCash as int --select @TotRevnu = sum(CASE WHEN total is null then 0 else total end) AS tot1 from RevnuView SET @TotRevnu = (select sum(CASE WHEN total is null then 0 else total end) AS tot1 from RevnuView) set @TotExpens = (select sum(case when total is null then 0 else total END)as tot2 from expensessview)

    Set @totalCash  =  @TotRevnu  - @TotExpens  
    if (@totalCash is null)
        BEGIN
          set  @totalCash = 0
        END
    ELSE
        BEGIN
          set  @totalCash = @totalCash
        END
    END
    EXEC @execute = CashFlowInsert ' عجز (فائض ) الايراد العام ' , @totalCash 
    -----------------------------------------------------------
    EXEC @execute = CashFlowInsert ' يتم تسويته بـ : ' ,' ' 
    -- المخصصات احمالى 

--- > Seconde Part declare @TotAllowances as int set @TotAllowances = (SELECT SUM(CASE WHEN (temp_budget.Debit - temp_budget.Credit) IS NULL THEN 0 ELSE (temp_budget.Debit - temp_budget.Credit) END) AS total FROM temp_budget INNER JOIN asset_ss ON temp_budget.Code = asset_ss.code WHERE (temp_budget.Code LIKE '24%')) if (@TotAllowances is null) BEGIN set @TotAllowances = 0 END else BEGIN set @TotAllwances = @TotAllowances
end END

    EXEC @execute = CashFlowInsert 'مخصص مكون خلال العام ' , @TotAllowances