1. Create a message with variable 
Patch: Application Developer/ Message/

Current Message Text:
The Customer Bill To on this Service Request has failed credit check. Please review and respond as appropriate.<br/>
<br/>
Service Request Identifier: SR#&V_SR_NUM<br/>
Customer: &V_CUSTOMER_NAME<br/>
Bill To Customer: &V_BILLTO_CUST_NAME<br/>
Customer Bill To Account Number: &V_BILLTO_ACCT_NUM<br/>
Initiating Business Unit: &V_BUSINESS_UNIT<br/>
Service Rep: &V_SR_CREATED_BY<br/>
<br/>
<br/>
<br/>
Note: This is an auto generated e-mail. Please do not reply.


2. use it in the PL/SQL program

      FND_MESSAGE.CLEAR;  --clear the message
      FND_MESSAGE.SET_NAME ('XXCS', 'XXCS_CREDIT_CHK_NOTIFICATION'); -- set message name
      fnd_message.set_token ('V_SR_NUM', i_sr_num);    --assign value to message variable
      FND_MESSAGE.SET_TOKEN ('V_CUSTOMER_NAME', V_CHR_CUST_NAME);
      FND_MESSAGE.SET_TOKEN ('V_BILLTO_CUST_NAME', V_BILLTO_CUST_NAME);
      FND_MESSAGE.SET_TOKEN ('V_BILLTO_ACCT_NUM', V_ACCOUNT_NUMBER);
      FND_MESSAGE.SET_TOKEN ('V_BUSINESS_UNIT', V_BUSINESS_UNIT);
      fnd_message.set_token ('V_SR_CREATED_BY', v_chr_created_by);
      v_message := FND_MESSAGE.GET; -- fetch the message text