Hi.
I found the answer of my question so I'll put it on the forum hoping that it helps others.
First of all I got the range of my cells:
error = CA_VariantSetCString (&MyCellRangeV, EXCEL_ARRAY_OF_CELLS);
error = Excel_WorksheetRange (ExcelWorksheetHandle, NULL, MyCellRangeV, CA_DEFAULT_VAL, &ExcelRangeHandle);
Second, I got the borders of my range cells into a handle:
error = Excel_GetProperty (ExcelRangeHandle, &ErrorInfo,Excel_RangeBorders, CAVT_OBJHANDLE,
&ExcelBorderHandle);
Now I get the bottom edge of my range cells into a handle:
status = Excel_BordersItem (ExcelBorderHandle, NULL,
ExcelConst_xlEdgeBottom,
&ExcelBorderHandleX);
Now, I change the line style of the bottom edge of my range cells:
error = Excel_SetProperty (ExcelBorder
HandleX, &ErrorInfo,Excel_BorderLineStyle, CAVT_VARIANT,
CA_VariantLong (1));
Finaly, I have changed the border weight of the bottom edge, of my range cells:
error = Excel_SetProperty (ExcelBorderHandleX, &ErrorInfo,Excel_BorderWeight, CAVT_VARIANT,CA_VariantLong (3));
Hope this helps.