In UserForm1 module:
Option Explicit
Public AbortProc  As Boolean

Private Sub CheckBox1_Click()
  Dim TestValue
  
  If AbortProc Then Exit Sub
  
  If CheckBox1 Then
    TestValue = 42
  End If
End Sub
and in other module:
Sub test()
  With UserForm1
    If Range("K4") = "N/A" Then
      .AbortProc = True
      .CheckBox1 = True    'Only want value changed, not the macro run as if the checkbox was clicked
      .AbortProc = False
    Else
      .CheckBox1 = False
    End If
    
    .Show
  End With
End Sub
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