Regular Expressions

Similar to my problem with converting a big chunk of validation into smaller chunks of functions I am trying to use Regular Expressions to handle the validation of many, many time fields.
 
I have a set of FormCalc scripts to calculate the various values for days, hours and the gain/loss of hours over a four week period. For these scripts to work the time format must be in HH:MM.
 
Accessibility guidelines nix any use of message box pop ups so I wanted to get around this by having a hidden/visible field with warning text but can't get it to work.
 
So far I have:
 
var r = new RegExp(); // Create a new Regular Expression Object
r.compile ("^[00-99]:\\] + [00-59]");
 
var result = r.test(this.rawValue);
 
if (result == true){
true;
form1.flow.page.parent.part2.part2body.errorMessage.presence = "visible";
}
else (result == false){
false;
form1.flow.page.parent.part2.part2body.errorMessage.presence = "hidden";
}