VBA Excel User Form Output to Txt File - vba

Question

I am trying to create a user form that takes user input and prints to a text file. I know the VBA scripting functions to print, store strings etc. BUT I'm new to userforms. How do you limit input and output to a text file? Add to that same file?
INPUT AND OUTPUT:
I would need to have this variety of
KEY FEATURES:
Limited Entry: XXXX means only enter 4 characters (The notepad file can only be certain characters long
Multiple Entries: After a set of records is entered to the text file, their values are stored and another input is allowed. Also the new entries have to be written to the same file on the next line
Space if left blank: If XXXX is left blank then four " " should be printed instead.
If you have part or all of these answers I'd like to hear from you!
---------------------------Edited with Adding Code-----------------------------
Private Sub Userform_Initialize()
'Fill Eggs
With Eggs
.AddItem "Eggs"
End With
End Sub
Private Sub CreateList_Click()
Dim myFile As String, myString As String
myFile = "C:\Reformatted.txt"
Open myFile For Output As #1
Dim fourChars As String * 4
fourChars = Milk.Value
myString = Eggs.Value + Milk.Value + Bread.Value
Print #1, myString
Close #1
Shell "C:\Windows\Notepad.exe C:\Reformatted.txt", 1
End Sub
So the above code launches this screen:

Answer 1

TextBox have MaxLength property. Default is set to 0 which does not limit character entry.
To limit the entry into a certain number, just change the value of this property to that number.
Now for replacing the XXXX with blank(if none or less than 4 is entered), take on SO advise in the comments.
Dim fourChars As String * 4
fourChars = TextBox1.Value
MsgBox Len(fourChars) ' will always return 4