Knowledge Base Articles » KB100207: How to Evaluate a VBScript Expression at Run Time.

The Eval function and the Execute statement which are new features in VBScript 5.0 are closely related. They both can be used to evaluate, or execute, a VBScript expression at run time.

Eval takes any valid VBScript expression as its argument. It is designed to be used in the form:

result = Eval(strValidVBScriptExpression)

If the argument is a valid VBscript expression, then Eval evaluates the code and sets result equal to the return value.

The Execute statement essentially behaves in the same way as Eval, but there are two crucial differences. First, Execute is used to execute expressions that DO NOT return a value. It is of the form:

Execute("strFact = ""DevGuru is great!""")

Second, if the argrument is of the form, a = b, then it is treated as an assignment operation where a is set equal to b. In contrast, Eval treats the form, a = b, as an equality comparison. It returns true if the comparison is true. Otherwise, it returns false.