Using SUBSTR and UPPER in IF Conditions in XML Pub RTF Template

Hello,

I am trying to use SUBSTR and UPPER functions in IF Conditions in XML Publisher RTF Template.

My requirement to hide the Supplier Site Address Line 1 in the Standard PO Document (We have created a RTF Template for this) if it starts with "ATTN:".

I have used below syntax but on running "PO Output for Communication", the request fails with Java / XML errors.

<?if:(xdofx:substr(upper(VENDOR_ADDRESS_LINE1), 1, 5)!='ATTN:')?>

Even removing "UPPER" and using just SUBSTR like below also fails.

<?if:(xdofx:substr(VENDOR_ADDRESS_LINE1, 1, 5)!='ATTN:')?>

Below is the section of the RTF Template where I am trying to do this: