VB Shift Cipher

[diamondw]

Hey,
i need some guidance.Im working on a project in vba(in excel).I am trying to create a shift cipher(example dog would be fqi)
i want the input to be in an input box(have that part) with the text to be shifted and amount that it will be shifted.The output will be in excel in a 20 column by n row array.I made a function to remove all non alphabetic lower case characters.This is what i have so far(theres a lot of things I just need help finishing and putting it all together).

[TEX]'Ask for dimensions of array and output numbers in array
Sub NumberArray()
    'this puts up input boxes and then stores the inputs to variables
    NumRows = InputBox("Input the number of rows.")
    NumColumns = InputBox("Input the number of columns.")
        For i = 1 To NumRows ' completes 1 row at a time
            For j = 1 To NumColumns 'goes through each column 1 at time
                Cells(i, j).Value = j + (i - 1) * NumColumns
            Next j
        Next i
End Sub

'change all letters to lowercase
'remove all non alphabetic characters
Function Remove(x)
    tempText = LCase(x) 'change all letters to lowercase
    
    For i = 1 To Len(x) 'len is number of characters in the script
    If Asc(Mid(tempText, i, 1)) >= 97 And Asc(Mid(tempText, i, 1)) <= 122 Then '97 is ascii a and 122 is ascii z
        tempOutput = tempOutput & (Mid(tempText, i, 1))
    End If
    Next i
    Remove = tempOutput 'outputs the text
End Function
 Function ShiftCipher(text, shiftamount)
 shiftamount = InputBox("Input how many numbers to shift by")
 Select Case letter
  Case "a"
    letter = Chr(97 + shiftamount)
  Case "b"
    letter = Chr(98 + shiftamount)
  Case "c"
    letter = Chr(99 + shiftamount)
  Case "d"
    letter = Chr(100 + shiftamount)
  Case "e"
    letter = Chr(101 + shiftamount)
  Case "f"
    letter = Chr(102 + shiftamount)
  Case "g"
    letter = Chr(103 + shiftamount)
  Case "h"
    letter = Chr(104 + shiftamount)
  Case "i"
    letter = Chr(105 + shiftamount)
  Case "j"
    letter = Chr(106 + shiftamount)
  Case "k"
    letter = Chr(107 + shiftamount)
  Case "l"
    letter = Chr(108 + shiftamount)
  Case "m"
    letter = Chr(109 + shiftamount)
  Case "n"
    letter = Chr(110 + shiftamount)
  Case "o"
    letter = Chr(111 + shiftamount)
  Case "p"
    letter = Chr(112 + shiftamount)
  Case "q"
    letter = Chr(113 + shiftamount)
  Case "r"
    letter = Chr(114 + shiftamount)
  Case "s"
    letter = Chr(115 + shiftamount)
  Case "t"
    letter = Chr(116 + shiftamount)
  Case "u"
    letter = Chr(117 + shiftamount)
  Case "v"
    letter = Chr(118 + shiftamount)
  Case "w"
    letter = Chr(119 + shiftamount)
  Case "x"
    letter = Chr(120 + shiftamount)
  Case "y"
    letter = Chr(121 + shiftamount)
  Case "z"
    letter = Chr(122 + shiftamount)
    End Select
    
    ShiftCipher = text + shiftamount
   
  
  
 End Function[/TEX]