Определить суммы длин отрезков. - VB

Option Explicit
Dim x1!, y1!, x2!, y2!, n%
Dim t1 As String, t2 As String
 
Private Sub cmdD_Click()
    Cls
    t1 = txt1.Text
    t2 = txt2.Text
    PSet (20, 1500)
    Print "Сумма длин отрезков"
    Print R(t1) + R(t2)
End Sub
 
Private Function R(t As String) As Single
    x1 = Val(t)
    n = InStr(t, ",")
    t = Mid(t, n + 1)
    y1 = Val(t)
    n = InStr(t, ",")
    t = Mid(t, n + 1)
    x2 = Val(t)
    n = InStr(t, ",")
    t = Mid(t, n + 1)
    y2 = Val(t)
    R = Sqr((x1 - x2) ^ 2 + (y1 - y2) ^ 2)
End Function