Run-time error "13" Несовпадение типов при работе с дробями - VB

Option Explicit
Dim x As Double
Dim y As Double
Dim xn As Double
Dim xk As Double
Dim dx As Double
Dim i As Integer
Dim NewLine As String
Dim STab As String
Sub Coordinats()
xn = TextLeft.Text
xk = TextRight.Text
dx = TextStep.Text
End Sub
Sub Tabuls()
    y = Sin(x)
End Sub
Private Sub mnuTab_Click()
NewLine = Chr(13) + Chr(10)
STab = Chr(9)
TextFun.Text = "X" & STab & "Y" & NewLine
Call Coordinats
For x = xn To xk Step dx
Call Tabuls
TextFun.Text = TextFun.Text & Str(Format(x, "0.00")) & STab + _
Str(Format(y, "0.0000")) & NewLine
Next x
End Sub
Private Sub mnuGraph_Click()
Dim CoordY, CoordX, sclx, scly, xpred, ypred
CoordY = PictureGraph.Height / 2
CoordX = PictureGraph.Width / 2
PictureGraph.Line (0, CoordY)-(PictureGraph.Width, CoordY)
PictureGraph.Line (CoordX, 0)-(CoordX, PictureGraph.Height)
Call Coordinats
 
If Abs(xn) > Abs(xk) Then
sclx = 0.5 * PictureGraph.Width / Abs(xn)
Else: sclx = 0.5 * PictureGraph.Width / Abs(xk)
End If
scly = 0.4 * PictureGraph.Width
For x = xn To xk Step dx
Call Tabuls
If x = xn Then xpred = x: ypred = y
PictureGraph.Line ((xpred * sclx + CoordX), (-ypred * scly + CoordY)) _
-((x * sclx + CoordX), (-y * scly + CoordY))
xpred = x
ypred = y
Next x
End Sub
Private Sub mnuClear_Click()
    TextFun.Text = ""
    PictureGraph.Cls
End Sub