Using the TI CellSheet Converter utility provided by Texas Instruments, it should be possible to transfer simple spreadsheets saved in Microsoft Excel format (.xls, .xlsx) to your TI device, including TI-NSpire. For other graphics calculators, the utility will convert it to other format suitable on that specific device.
Convert Microsoft Excel Open XML workbook and spreadsheet to TI-Nspire document.
We have found one software suitable in our database for this conversion.
Microsoft Windows software - convert xlsx to tns on Windows
A converter for transfer spreadsheets to TI calculators
Convert from xlsx file format
The table with program actions contains information about what each program is capable of doing with their files. This may be a good pointer for further searches for certain file conversions and help you find the converter you are looking for if our search result is insufficient for you. However, it is far from perfect and may sometimes show results which are not really usable because of the nature of the software handles the files. So a conversion that appears as possible, just because of matched actions, may in fact not be possible.