Argentina Withholding Tax - RFWT0010

I am new to Argentina withholding taxes and trying to develop a process to update the vendor master and open items. We currently perform the steps manually and it's very time-consuming and prone to errors. We receive a file from the govt with the rates per tax number (CUIT) each month. Is there a standard program to upload the file, perform a comparion of the rates on the master record and update the tax code on the master record?

I have not been successful in getting RFWT0010 to change the withholding tax code on the open line items when I change the withholding tax code on the vendor. We have extended withholding. Tax Type I1 is used for withholding tax and then we have different tax codes representing different rates. A vendor might be I1 with tax code IM that has rate of 3% but we need it changed to I1 with IN tax code so it's 2%. I ran RFWT0010 but it doesn't change the tax code from IM to IN on the open items. I can get the program to delete or add a withholding tax type but it won't change a withholding tax code on an existing type. Any suggestions on what I'm doing wrong or steps I'm missing?

Thank you,

Kathy