step-1 create your own "save" button like-- 'change rate'

step-2 create a hidden dummy item like-- P10_REFNO , VALUE PROTECTED SHOULD BE OFF

step-3 create dynamic action name--> get selected refno
event- selection change[interactive grid]
action- javascript code

code--

var i, REF_NOS = "",

model = this.data.model;

for ( i = 0; i < this.data.selectedRecords.length; i++ ) {

REF_NOS += model.getValue( this.data.selectedRecords[i], "REFRENCE_ID") + ":";

}
REF_NOS= REF_NOS.substr(0,REF_NOS.length-1);
apex.item('P10_REFNO').setValue(REF_NOS);
//console.log(REF_NOS);
note---- "REFRENCE_ID" SHOULD BE YOUR PRIMARY KEY COLUMN

step-4 create a process name--'update rate' SERVER SIDE CONDITION-- WHEN BUTTON PRESSED-- 'change rate'

BEGIN

FOR REC IN (SELECT REF_NO,new_rate ,old_rate FROM XYZ WHERE REF_NO IN (select column_value from apex_string.split(:P10_REFNO, ':')))
LOOP

if REC.old_rate > 0 and REC.new_rate > REC.old_rate then
UPDATE TABLE A
SET audit_yn='Y',
audit_date=to_date(sysdate,'dd/mm/rrrr'),
auditor=:APP_USER,
authority=XYZ',
auth_date=to_date(sysdate,'dd/mm/rrrr'),
auth_yn='Y'
WHERE ref_no = REC.REF_NO and to_date(to_char(ref_date,'dd/mm/yyyy'),'dd/mm/yyyy') = to_date(:ref_date,'dd/mm/rrrr');

else
UPDATE A
SET audit_yn='Y',
audit_date=to_date(sysdate,'dd/mm/rrrr'),
auditor=:APP_USER

end if;
END LOOP;
END;

at the report region keep this html code at "Header and Footer section"

Header Text
<div style="text-overflow:ellipsis;overflow:auto;white-space:nowrap">
Footer Text
</div>

you can also use the success message section of built in interactive gride process