Cannot convert to double

So here is my program. I was instructed to make a program that creates basically a reciept for someone who buys sofa's and chair's (furniture store.) You had to have them fill in their address and state, city, zip etc. While trying to do so I've come across errors saying that it cannot convert my address and city/zip to a double. I assume it is because I have to enter numbers in the address line and state/city/zip, and I have it as a string so it can't convert it. Please help me fix my program as it is due tomorrow.
<3



Public Class Form1

Private Sub btnClear_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnClear.Click
lstOrderForm.Items.Clear()
End Sub

Private Sub btnEnter_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnEnter.Click
Dim numofsofa, numofchair, chair, sofa, tax, zip As Double
Dim name, statecity, address As String

DataIn(numofsofa, numofchair, statecity, name, address, zip)
CalculateNewValues(sofa, chair, numofsofa, numofchair, tax)
Output(sofa, chair, address, name, statecity, numofsofa, numofchair, tax, zip)

End Sub
Sub DataIn(ByRef numofsofa As Double, ByRef numofchair As Double, ByRef statecity As String,
ByRef name As String, ByRef address As String, ByRef zip As Double)

numofsofa = CDbl(txtSofa.Text)
numofchair = CDbl(txtChair.Text)
statecity = CStr(txtLocation.Text)
name = CStr(txtName.Text)
address = CStr(txtAddress.Text)
zip = CDbl(txtZip.Text)
End Sub

Sub CalculateNewValues(ByVal numofsofa As Double, ByVal numofchair As Double,
ByVal sofa As Double, ByVal chair As Double, ByVal tax As Double)

sofa = numofsofa * 925
chair = numofchair * 350
tax = (sofa + chair) * 0.5
End Sub

Sub Output(ByVal sofa As Double, ByVal address As String, ByVal chair As Double,
ByVal name As String, ByVal statecity As String, ByVal numofsofa As Double, ByVal numofchair As Double,
ByVal tax As Double, ByVal zip As Double)

lstOrderForm.Items.Add("Inovice Number: FIXNUMBER!!!")
lstOrderForm.Items.Add("")
lstOrderForm.Items.Add("")
lstOrderForm.Items.Add("Name: " & name)
lstOrderForm.Items.Add("Address: " & address)
lstOrderForm.Items.Add("City: " & statecity)
lstOrderForm.Items.Add("Zip: " & zip)
lstOrderForm.Items.Add("")
lstOrderForm.Items.Add("Number of Chairs: " & numofchair)
lstOrderForm.Items.Add("Number of Sofas: " & numofsofa)
lstOrderForm.Items.Add("")
lstOrderForm.Items.Add("Cost: " & FormatCurrency(sofa + chair))
lstOrderForm.Items.Add("Sales Tax: " & FormatCurrency(tax))
lstOrderForm.Items.Add("----------")
lstOrderForm.Items.Add("Total Cost: " & tax + chair + sofa)



End Sub


Private Sub btnQuit_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnQuit.Click
Dim Response As DialogResult
Response = MessageBox.Show("Do you really want to exit?", "", _
MessageBoxButtons.YesNo, MessageBoxIcon.Question)
If Response = DialogResult.Yes Then
Me.Close()
End If
End Sub
End Class