Cant undefine a variable

[HackinHoodLogicsTm]

Please i need help.
I have defined a Date Variable. As follows

[syntax=neobook]DefineVar "[1st]" "Date" "mm/dd/yyyy" "Global" "[MonthNum]"/01/[Year]"
[/syntax]

The above code works fine..
Now i want to undefine the "[1st]" variable and define another date variable into it.

This is how i undefine varaiable "[1st]"
ClearVariable "[1st]"

Then i get this error
"" is not a valid date value.

Please i need your help on this.
Thanks

[Gaev]

HackinHoodLogics:

From the Help file ...

In order to delete a variable created with DefineVar, you must first re-declare the variable as “Undefined”, then clear it with SetVar. For example:

DefineVar "[Birthdate]" "Undefined" "" "Global" ""
SetVar "[Birthdate]" ""

[HackinHoodLogicsTm]

Thanks...that works