Userforms to populate cells

[Waterpolo1]

I have a user form with 3 questions.

1.) Thickness (this selects the correct sheet I have e.g "6-8mm", "10-12mm").
2.) Number of defects. From question 1, this number here is inputed into the correct work sheet.
3.) Number of people. Same as questions 2; this number here is inputed into the relevant cell on the worksheet selected in question 1.

I have the following code but it doesn't appear to work:-

Private Sub Submitbutton_Click()
Sheets("ListBox1.Value").Range("B20").Value = Me.tbdefect.Value


End Sub

 

[CalcSux78]

Sheets("ListBox1.Value") should be Sheets(ListBox1.Value)
The way it's currently entered, excel is looking for a sheet named "ListBox1.Value" and isn't finding it.