The above solution will work but it has to open the workbook. If you are not willing to do that, VB code will be an another option. Try this code and let me know if this helps @prashantP
Dim excel As Microsoft.Office.Interop.Excel.Application
Dim wb As Microsoft.Office.Interop.Excel.Workbook
Dim ws As Microsoft.Office.Interop.Excel.Worksheet
excel = New Microsoft.Office.Interop.Excel.Application
wb = excel.Workbooks.Open("D:\UiPath\CopyAndPasteInExcel\samplefile.xlsx", [ReadOnly]:=False)
excel.Visible = True
ws = CType(wb.Sheets("SSMS Script"), Microsoft.Office.Interop.Excel.Worksheet)
ws.Activate()
Dim str As String = ws.Shapes.Range("TextBox 1").AlternativeText
system.Windows.MessageBox.Show(str)
wb.Close
excel.Quit