Thanks for the hint with the button, I didn't manage to solve it with string comparison but with this:
Code:
<Text Name="ClockSignal" Visible="false" DynamicData="/GameData.General.Time" Size="0,0" orig="Parent.UpdateData.press=true" OnTextChanged="
OnTextChanged=''
Parent.UpdateData.press=true
"></Text>
<Button Name="UpdateData" Visible="false" OnPress="
<here comes the code that should not get executed twice>
Parent.ClockSignal.OnTextChanged=Parent.ClockSignal.orig
" />
However using this method I do get the variable name again and not its content. But at least I got a step forward to fix the problem.