Gembox Excel and Listboxes not getting along

[habydlg]

I am currently using Gembox to pass text to excel and I have a problem. I have imported the required resources but when I try to pass an item in a list box it comes to an error... here's my code

'checkrow is a number loaded from that same excel
Dim ef As ExcelFile = New ExcelFile
ef.LoadXls("C:\Users\DF\Desktop\registro_prestamos.xls")
Dim ws As ExcelWorksheet = ef.Worksheets(0)
checkrow = (ws.Cells("F2").Value.ToString())
 
'numrent is a number to keep track of which item to load
ws.Cells("B" + (Str(checkrow).Trim)).Value = listbox.Items(numrent).Value.ToString

it throws an error stating "Public member 'Value' on type 'String' not found." Any ideas why?