Thank you for using Syncfusion products.
XlsIO supports external reference on exporting. But we are not clear with your scenario on excel export. Could you please let us know whether you are exporting to Pdf or DataTable or from grid to excel? Also, let us know your current and expected outputs as a screen-shot. This will be helpful in defining your requirement and provide a valid solution on that.
Please let us know if you need any clarification.
By default while exporting the grid control it will export the cell value, you can handle that by using the cell export event handlers as shown in the following code snippet,
grid.ExportToExcel("Sample.xls", ExcelVersion.Excel97to2003, CellExportingHandler);
In the CellExpotingHandler method you can provide necessary formula to the particular cell range to make it work.Please find the CodeSnippet for CellExportingHandler.
e.Range.CellStyle.Font.Size = 12;
e.Range.CellStyle.Font.FontName = "Segoe UI";
//You can provide necessary formula here inorder to move to another worksheet
e.Range.Formula = " =Sheet1!A3";
e.Handled = true;