Change value in non editable attributes?

Hello!

I have created a report that takes 2 inputs (attrubute type nr, new value). The report is started on an object, and should change the value of the attrubute with the right attribute type nr to the new value.

It works fine for some attributes like "Short desc" but when it comes to "External ID" it putts out an ERROR saying "String index out of range: 36"

Is it because it is a read only attribute?

BR!