請教一個SQL語法..(編號:1740)

declare @nstring char(60),@bint int,@CompNo char(2)
set @CompNo='QC'
set @nstring = "declare @mint int" +
"set @mint = (select count(*) from Ac" + @CompNo + "Bank) "
exec (@nstring , @bint = @mint output)
print @bint
錯誤是.."Line 5: Incorrect syntax near ','."
請問如何把 exec () 處理的結果傳出來