One way is to set the condition node to be 'Custom' and use this code:
return StringUtils.isNumeric(source.getNode('PID-3'.1));
This will look at the field in the source message and, if it is just numbers, return true. Otherewise, it will return false, which will cause the condition to fail.
![](https://www.qvera.com/kb/?qa=blob&qa_blobid=11396727881362792156)