key = 7

Print "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz"

'Encrypt the text
Print CaesarCypher$("ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz", key)

'Decrypt the text by changing the key to (26 - key)
Print CaesarCypher$(CaesarCypher$("ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz", key), (26 - key))

Function CaesarCypher$(string$, key)
    If (key < 0) Or (key > 25) Then _
    CaesarCypher$ = "Key is Ouside of Bounds" : Exit Function
    For i = 1 To Len(string$)
        rotate = Asc(Mid$(string$, i, 1))
        rotate = (rotate + key)
        If Asc(Mid$(string$, i, 1)) > Asc("Z") Then
            If rotate > Asc("z") Then rotate = (Asc("a") + (rotate - Asc("z")) - 1)
        Else
            If rotate > Asc("Z") Then rotate = (Asc("A") + (rotate - Asc("Z")) - 1)
        End If
        CaesarCypher$ = (CaesarCypher$ + Chr$(rotate))
    Next i
End Function