So, I downloaded the source code and found where SUBSTITUTE was translated to REEMPLAZAR instead of SUSTITUIR, and -maybe- fixed it.
Here's a patch for translation-updates-20100219. -- Love, Marga
--- - 2010-04-22 17:26:31.613722574 +0000 +++ /tmp/bzdiff.XXXX6RkYPO 2010-04-22 17:26:31.000000000 +0000 @@ -145359,7 +145359,7 @@ formula source\core\resource\core_resource.src 0 string RID_STRLIST_FUNCTION_NAMES SC_OPCODE_TEXT 0 en-US TEXT 2002-02-02 02:02:02 formula source\core\resource\core_resource.src 0 string RID_STRLIST_FUNCTION_NAMES SC_OPCODE_TEXT 0 es TEXTO 2002-02-02 02:02:02 formula source\core\resource\core_resource.src 0 string RID_STRLIST_FUNCTION_NAMES SC_OPCODE_SUBSTITUTE 0 en-US SUBSTITUTE 2002-02-02 02:02:02 -formula source\core\resource\core_resource.src 0 string RID_STRLIST_FUNCTION_NAMES SC_OPCODE_SUBSTITUTE 0 es REEMPLAZAR 2002-02-02 02:02:02 +formula source\core\resource\core_resource.src 0 string RID_STRLIST_FUNCTION_NAMES SC_OPCODE_SUBSTITUTE 0 es SUSTITUIR 2002-02-02 02:02:02 formula source\core\resource\core_resource.src 0 string RID_STRLIST_FUNCTION_NAMES SC_OPCODE_REPT 0 en-US REPT 2002-02-02 02:02:02 formula source\core\resource\core_resource.src 0 string RID_STRLIST_FUNCTION_NAMES SC_OPCODE_REPT 0 es REPETIR 2002-02-02 02:02:02 formula source\core\resource\core_resource.src 0 string RID_STRLIST_FUNCTION_NAMES SC_OPCODE_CONCAT 0 en-US CONCATENATE 2002-02-02 02:02:02