prevent checkbox from being selected in Java script

i have a java script function that checks if a check box is checked, if yes count how many check boxes are checked and if the max number of 4 is reached. The thing is how can i make that when the 5 checkbox is checked i want to show an alert and than disable all the unchecked check boxes, even the one that was tried to be checked as the 5 one.

 function ChkValidate() {

          var chkDytLek = document.getElementById("ChkDytLek");
          var chkDytUSD = document.getElementById("ChkDytUSD");
          var chkDytEU = document.getElementById("ChkDytEU");
          var chkDytCAD = document.getElementById("ChkDytCAD");
          var chkDytCHF = document.getElementById("ChkDytCHF");
          var chkDytAUD = document.getElementById("ChkDytAUD");
          var chkDytGBP = document.getElementById("ChkDytGBP");

          var MaxCount = 0
          var unCheckedCount = 0

          if (chkDytLek.checked == true) {
              MaxCount = MaxCount + 1

              if (MaxCount == 4) {

                  disableIfNotChecked();
              }
          } else {
              unCheckedCount = unCheckedCount + 1 
          }

          if (ChkDytUSD.checked == true) {
              MaxCount = MaxCount + 1

              if (MaxCount == 4) {
                  disableIfNotChecked();
              }
          } else {
              unCheckedCount = unCheckedCount + 1
          }  
          if (ChkDytEU.checked == true) {
              MaxCount = MaxCount + 1
              if (MaxCount == 4) {
                  disableIfNotChecked();
              }
          } else {
              unCheckedCount = unCheckedCount + 1
          }

          if (ChkDytCAD.checked == true) {
              MaxCount = MaxCount + 1

              if (MaxCount == 4) {
                  disableIfNotChecked();
              }
          } else {
              unCheckedCount = unCheckedCount + 1
          }

          if (ChkDytCHF.checked == true) {
              MaxCount = MaxCount + 1

              if (MaxCount == 4) {
                  disableIfNotChecked();
              }
          } else {
              unCheckedCount = unCheckedCount + 1
          }
          if (ChkDytGBP.checked == true) {
              MaxCount = MaxCount + 1

              if (MaxCount == 4) {
                  disableIfNotChecked();
              }
          } else {
              unCheckedCount = unCheckedCount + 1
          }

          if (ChkDytAUD.checked == true) {
              MaxCount = MaxCount + 1

              if (MaxCount == 4) {
                  disableIfNotChecked();


              }
          } else {
              unCheckedCount = unCheckedCount + 1
          }

           if (unCheckedCount >= 4) {                  
              enableIfNotChecked();
           }


      }

the current code displays an alert and disables the checkboxes when the count is 4, when i want this to happen at the 5 one, but if i change

 if (MaxCount == 4) {
                  disableIfNotChecked(); 

to:

 if (MaxCount == 5) {
                  disableIfNotChecked();

the code will disable the check boxes but will also check the one that was selected as the 5.

any idea how can i give a solution to this situation?