To center additional header lines using WordRpt_SetHeader() from WordReport.fp, insert a tab at the start of each line after the first.
For example, modify the wordrpt.prj sample that ships with CVI to the following:
char rptHeader[400];
...
sprintf(rptHeader, "Line 1\n\tLine 2\n\t"
"Line 3\n\tLine 4\n\t"
"Line 5");
WordRpt_SetHeader (docHandle, "", rptHeader, "", WRConst_FieldDate,
WRConst_FieldEmpty, WRConst_FieldTime);