>>> add periods to names <<<
Did you read the line above????????????????
Form2TextboxText becomes Form2.Textbox.Text
Form2TrackBar2Value becomes (you can figure it out, can't you?)

If you change this code using the hints above it will get you started.

Code:
    Private Sub setTrackBar()
        If Not IsNumeric(Form2TextboxText) Then
            'textbox is not number
            Debug.WriteLine("NOT A NUMBER")
            Exit Sub
        End If
        Dim asDecimal As Decimal = Decimal.Parse(Form2TextboxText)
        Dim asInteger As Integer = Convert.ToInt32(Math.Ceiling(asDecimal))
        Select Case Form2TextboxText 'textbox is string
            Case "1.0" 'this is string 
                Form2TrackBar2Value = 1000
            Case Else
                If asInteger > 0 AndAlso asInteger <= 999 Then
                    Form2TrackBar2Value = asInteger
                Else
                    Debug.WriteLine("number not between 1 and 999 inclusive")
                End If
        End Select
    End Sub
and for the record, we don't 'need' or 'have' to do anything. The problem isn't us.