Input box to sum and display sum as msgbox

Hello I am struggling to make this assignment happen:Create a macro procedure that asks for three integers (one at a time) and displays their sum in a message box.
Insert a module into the project, then insert a macro procedure named AddThreeNumbers. Code this procedure so that when it is executed, it will ask for three integers (one at a time), store them into three variables respectively, computes their sum, and display “The sum of [1st num], [2nd Num], and [3rd Num] is [the sum of the three numbers].” where each square bracket should be replaced by the numbers that the user put in. That is, if the user put in 10, 20, and 30 into the three boxes, it should display “The sum of 10, 20, and 30 is 60.” Make sure you declare and use appropriate variables.
1. The message box should have the title, “My Own Adder”.
2. Insert an ActiveX Command button displaying a picture of your choice, with the caption, “I Add Three Integers.”
3. Link the AddThreeNumbers procedure to the button so that when the button is clicked, the procedure is executed.
4. Save and submit the workbook.
I currently have this code but my input boxes are not being saved as a variable.

Private Sub CommandButton1_Click()
Dim myValue As Integer
myValue = inputbox("Enter first interger")
Dim myValue2 As Integer
myValue2 = inputbox("Enter second interger")
Dim myValue3 As Integer
myValue3 = inputbox("Enter thrid interger")
MsgBox ("The sum of" & myValue ", " & myValue2 ", " & myValue3 "Is SUM(myValue, myValue2, myValue3)")
End Sub

Now I am getting an error message in my msgbox code when I add the Sum function. Addtionally, I still get the words "myValue..." in the message box not the numbers entered into the inputbox.