Finds Breaks In The Values

I have a macro that needs to walk down a list of values and when it finds breaks in the values, it will insert a formula for a calculation. The problem I'm having is getting the code to loop correctly until it finally finds the value "End" when it should stop (when I play around with the code, sometimes I can get it to continue the loop, but it blows past "End" and then it experiences an error because it can't end.

Sheets("Master").Select
Range("B1").Select
ActiveCell.Offset(1, 0).Select
AssetIDStartRange = ActiveCell.Address
X = 0
Do
ActiveCell.Offset(1, 0).Select
X = X + 1
Loop Until ActiveCell.Value ""
SortCriteriaName = ActiveCell.Value
ActiveCell.Offset(-1, 1).Select
ActiveCell.Formula = "=SUMIF($B13:$B5000," & """" & SortCriteriaName & """" & ",$H$13:$H$5000)"
ActiveCell.Offset(0, -1).Select

If ActiveCell.Value "End" Then....................