asp instr,Replace,isNumericメソッド

                    tid=Request.QueryString("id")
                    tableName="P_T_JIUYU_JYPL" 
                    'instr   indexof   
                    if Instr(1, tid, "dxcl_")>0 then
                       tid=Replace(tid,"dxcl_","") 
                       tableName="P_T_JIUYU_DXCL" 
                    end if
                    if Instr(1, tid, "jypl_")>0 then
                        tid=Replace(tid,"jypl_","") 
                        tableName="P_T_JIUYU_JYPL" 
                    end if
                    if not IsNumeric(tid) then
                        tid=-1
                    end if