Custom fields ordering of Options

Hi,

We have a multi-select custom field added in, which has a number of options which are stored as the following list:
1,optD
2,optB
3,optC

We have test cases that have used this field and populated one of the values as relevant.
Say Test Case 1 : optB

Now, I tried re-arranging the field value options to:
1,optB
2,optC
3,optD

What has happened in this case, is that custom field value for Test Case 1 changed from optB to optC - persisting the serial number of the option, rather than the actual option value.

So the above way of ordering does not work.

Is there a way to re-order the options without mixing up values in our current test cases?