Etydhv

I was trying to use DynamicModule to create a Input cell that contains a variable assignment, where the variable name is given by a InputField. A minimal example is:

createExample[] := DynamicModule[name = Null,
 Column[
 InputField[Dynamic[name]],
 Button["OK",
 With[name1 = name,
 CellPrint[ExpressionCell[
 Defer[name1 = 99999]
 , "Input"]]]
 ]
 ]
 ]

Running createExample[] will give

Enter a variable name called var1 and click OK button

However, when I evaluate this assignment, the InputField also changes

My question is, how to avoid the change of the variable inside the DynamicModule.

If you work with Boxes you don't have to worry about evaluations:

createExample[] := DynamicModule[name="",
 Column[
 InputField[Dynamic[name],Boxes, ContinuousAction->True],
 Button[
 "OK",
 Dynamic @ CellPrint[Cell[BoxData[RowBox[name, "=", "99999"]], "Input"]]
 ]
 ]
]

A short animation:

In your code name1 is not localised within the scope of the DynamicModule. Try your experiments on these two variations.

 createExample2[] := 
 DynamicModule[name = Null, 
 Column[Dynamic@name1, InputField[Dynamic[name]],
 Button["OK", With[name1 = name, 
 CellPrint[ExpressionCell[Defer[name1 = 99999], "Input"]]]]]];

 createExample3[]:=DynamicModule[name = Null, name1, 
 Column[Dynamic@name1, InputField[Dynamic[name]],
 Button["OK", With[name1 = name, 
 CellPrint[ExpressionCell[Defer[name1 = 99999], "Input"]]]]]]; 

Here's a different way to inject the value of name into the cell:

createExample[] := DynamicModule[name = Null,
 Column[
 InputField[Dynamic[name], Hold[Expression]],
 Button["OK", 
 name /. Hold[v_] :> CellPrint[ExpressionCell[Defer[v = 99999], "Input"]]]
 ]
 ]

The reason var1 becomes 99999 in the OP's code, is that the displayed contents of the InputField is the dynamically updated value of name. When name is set to var1, it displays the value of var1. Initially, it has no value, so we set var1. But when a value for var1 is set, the value is displayed. The above prevents that by specifying the type of the contents to be a held expression. "Held" means that it won't be evaluated. It also means that the value of name will be Hold[var1] when var1 is entered into the field. To handle this, I opted for the alternative method of injecting the user's input into the Set command in the cell.