Hi Gill,
You could try to fix this with E-Catts.
Even if it is not their main goel, it can be used for this.
This is quite simple to deal with.
Transaction secatt.
Create a test script, in the Editor tab, click on pattern.
then select UI control / TCD(record), pick your transaction in the fill then execute.
You'll have to do the work for one customer.
Then once you're done, after save, you should be back to secatt tranacation. Pick yes to the transfer data question.
Then double click in the editor on XD02_01.
Expanse the following nodes: Dynpro / [1] then double click on FIELD.
you should find here the customer number you filled.
On the line you should have for example: 'S' 'RF02D-KUNNR' 6000001
S is for set new value.
You have to change the customer number by a variable named for exampl I_KUNNR, press enter then select import parameter.
You can now save your test script. Exit to secatt transaction then create a Test configuration.
In configuration tab fill your test script name then go to Variants tabs.
You will find a screen where you can fill a line for each customer you want to deal with. (you can also use an excel file)
Good luck.
Do not hesitate if you have questions