'Journal of Online Mathematics and Its Applications
'Volume 7, December 2007
'
'Write Your Own Excel Mathlets
'Christoph Maier

'Visual Basic Code for the Macros

Sub move_right()
	'-----------------------------------------------
	' move_right Macro
	' moves Xo right by .02
	' Keyboard Shortcut: Ctrl+Shift+R
	'----------------------------------------------
	' Get the current value of Xo
	' the value in critical cell d2
	current = Range("d2").Value
	'
	' assign a value of 0.02 to delta
	delta = 0.02
	'
	' Add delta to Xo if Xo + delta <= 8.01
	If current + delta <= 8.01 Then
		Range("d2").Value = current + delta
	End If
End Sub

Sub move_left()
	'-------------------------------------------------------
	' move_left Macro
	' moves Xo left by .02
	' Keyboard Shortcut: Ctrl+Shift+L
	'-------------------------------------------------------
	' Get the current value of Xo
	' the value in critical cell d2
	  current = Range("d2").Value
	'
	' assign a value of 0.02 to delta
	  delta = 0.02
	'
	' Add delta to Xo if Xo - delta >= -.01
	If current - delta >= -0.01 Then
		Range("d2").Value = current - delta
	End If
End Sub

Sub choose_x_value()
	'
	'----------------------------------------------------
	' choose_x_value macro
	' allows the user to skip to a desired x-value
	' Macro recorded 7/16/04
	' Keyboard shortcut Ctrl+g
	'----------------------------------------------------
	' Set prompt.
	Message = "Go to x (rounded to the nearest .02) = ?  "
	' Set title.
	Title = "Choose x-value"                                                            
	' Display message and title.
	myvalue = InputBox(Message, Title)
	'
	'Round myvalue to the nearest .02
	roundedvalue = Round(myvalue / 2, 2) * 2
	If (Abs(roundedvalue - myvalue) > 0.0000005)  Then
		x = MsgBox("Your value was rounded to the nearest .02", vbOKOnly, "Warning")
		myvalue = roundedvalue
	End If
	'
	' If x-value is between 0 and 8 (inclusive) change x-value
	' in cell D2 to desired value
	If (myvalue >= 0 And myvalue <= 8) Then
	    Range("D2").Value = myvalue
	End If
End Sub