create new column in excel file and add data from a .DAT file to it VB.Net

Question

This might be too much of a general question as I have yet to write code. I am just looking for some advice tips and tricks for how to go about my problem.

I am looking to create a UI using VB.Net which allows me to create a new column in an uploaded excel file and add specific data from a .DAT file to it.

There is only 1 sheet in the uploaded excel file. The info I want from the .DAT file is got by using data in a specific column in the excel file then finding the same data in the .DAT file and taking characters in position eg.123

If anybody knows if this is possible or the best way to go about coding it that would be great as I am open to learning new things and any help I can get :-)

Thanks

Protected Sub ReadDat(sender As Object, e As EventArgs)

    For Each lines As String In File.ReadLines(Server.MapPath("~/Files/test.dat"))

         If lines.Contains("xyz")  AndAlso lines.Substring(12, 3) Is "123" Then          
                
             MsgBox(lines)

         End If
     Next

 End Sub