We are not clear with your requirement. As far we have understood, you can set a named range for the cells you wanted to access. The following code example illustrates this behavior.
//Adding named range to the workbook
IName workBookName = workbook.Names.Add("WorkBookName");
workBookName.RefersToRange = worksheet.Range["A1"];
//Looping through the Named Ranges in a workbook.
We have shared a sample for your reference which can be downloaded from following link
To know more about named range in XlsIO, kindly go through the following UG documentation link
UG Documentation link: http://help.syncfusion.com/file-formats/xlsio/working-with-formulas#defined-names
The provided sample may help you if your requirement is similar. If not, please share us the requirement in detail to provide the solution at the earliest.
The possible ways to access a cell or a range in a worksheet is explained briefly in the following UG documentation link. Kindly refer to this and let us know if this helps.
If still you are not able to achieve your requirement, please share us a model or a screen-shot explaining your behavior, which will help us to provide a prompt solution.