methods - Running a command once time has been met only once in c# using timer -

i trying invoke message box once time 5pm. once time 5pm , messagebox has showed. want set bool value false whole day. until not next day messagebox shouldn't show. searched on website not finding answer.

using system; using system.collections.generic; using system.componentmodel; using system.data; using system.drawing; using system.linq; using system.text; using system.windows.forms;   namespace iqa {     public partial class form1 : form     {         private system.threading.timer timer;          public form1()         {             initializecomponent();         }          private void form1_load(object sender, eventargs e)         {             this.text = "i[q]a";             timer1.enabled = true;             timer1.interval = 1000;              timer1.tick +=new eventhandler(timer1_tick);          }          private void button1_click(object sender, eventargs e)         {             //messagebox.show("the current time is: " + datetime.now.tostring("h:mm"));         }          private void timer1_tick(object sender, eventargs e)         {             if (datetime.now.tostring("h:mm") == "7:57" && ran == false)             {                 messagebox.show("it 7:55");                 ran = true;                     // after message box has shown once still keeps popping up. way stop              }             else             {                  // nothing             }         }      } }