Customer Group Wise Credit Limit

There is a scenario where I’ve Created One Customer Group Abc in That There are Two individual Customers Abc1 and Abc2.
A credit Limit of 1,00,000 has been Set in The Customer Group, after That I’ve Created one Transaction of 1,00,000 for Abc1,
But when I Tried to Create a Transaction of 80,000 for Abc2 System won’t Stop me To create that but it should Does, Bcz Limit has been already Set for 1,00,000 in the Customer Group which is exceeded by Abc1
then Why Should System Allow me to create a Transaction of 1,80,000 for That Abc Customer Group?
Please Help Me Out of This if Any Guidance or Solution available

It is an Important Scenario for Business Please Help me With this if There Is a Client Script required.