A VCE Variable is normally a numerical value. Before you can use a variable, you must state it by using 'VCE_modVariable'. The first parameter is the object of which the variable shall belong to, the 2nd parameter is the name of the Variable, the 3rd parameter is what you are doing to that variable, and the 4th parameter is how much you wish to change it.
Afterwards, you can use an 'ifVariable' event to check the value of the variable. 'onVariableTrue' means if the statement is a true statement, and 'onVariableFalse' is just the opposite.
I am a huge VCE user, so I can answer most questions.