So I'm working with subs

I need three subs.
Input, Processing and Output.

I got something for Input and Processing. I don't know if input is right, but first let me say the PROGRAM WORKS. It calculates right and give me what I need. But I was just asked to have 3 one for each IPO.

Again my program works. Here it is:

Public Class MainForm

Private Sub btnExit_Click(sender As Object, e As EventArgs) Handles btnExit.Click
Me.Close()
End Sub

Private Sub btnCal_Click(sender As Object, e As EventArgs) Handles btnCal.Click
Call Input()
Call Calculate()
End Sub

Private Sub Input()
Dim Len As Decimal = 0
Dim Wid As Decimal = 0
Dim Hei As Decimal = 0
Dim Cov As Decimal = 0
Dim Rolls As Decimal = 0
End Sub

Private Sub Calculate()
lblRolls.Text = txtLen.Text * txtWid.Text * txtHei.Text / txtCov.Text
End Sub
End Class


This is originally what I had for the Output sub:
lblRolls.Text = Convert.ToString(Rolls)

(Rolls) kept getting a blue error line because it was not declared.
Now this is completely wrong to use for the output I get that now.
And I'm honestly not worried about having in my program seeing how the program does exactly what I need but any advice would be great thanks.