VBA-Excel: Subtract date and time from two NOWs and display it in a textbox

Hello ALL,

I am trying to create a VBA code that calculates elapsed time after a certain action checkbox is clicked.

On clicking checkbox1 NOW is captured and display in textbox1.
on clicking checkbox2, NOW is displayed in textbox3 and the elapsed time (value in textbox3 - value in textbox1) needs to be displayed in textbox4 in hours and minutes format accurately. Which i am unable to do after trying and googling for different codes.
I have remained on and off with VBA, so i am not fluent. Can someone help me with the piece of code?

Dim X1 As Date

Private Sub CheckBox1_Click()

X1 = Now

If CheckBox1.Value = True Then TextBox1.Value = Now
If CheckBox1.Value = False Then TextBox1.Value = Null

If CheckBox1.Value = True Then TextBox2.Value = "00:00"
If CheckBox1.Value = False Then TextBox2.Value = Null

End Sub

Private Sub CheckBox2_Click()

Dim X2 As Date
Dim X3 As Date
Dim X4 As Date

X2 = Now

If CheckBox2.Value = True Then TextBox3.Value = Now
If CheckBox2.Value = False Then TextBox3.Value = Null
If CheckBox2.Value = False Then TextBox4.Value = Null

X3 = X2 - X1
TextBox4.Value = X3

End Sub