Hi @ovidiu_2088,
As @Jobin_Joy mentioned, the error you are getting is because one of your variables is null. I would imagine it’s down to either row.item("Value") or ResultRGX being null, ResultRGX is more likely to be null.
Try running your workflow in debug, allow the code to throw the Object Reference error and then look at the Locals panel for your null variable. If it’s ResultRGX, you may need to alter your Regex pattern. If it’s row.item("Value"), check that your DataTable dtData is being picked up correctly and there is data present in the DataTable