Regular Expression - Javascript validation

Hi all

this should be easy. I'm probably missing something really basic.

Here's the deal: 16 digit number for the respondent to enter. I have set up 4 text fields allowing 4 characters each (they are text fields because at least 3 of the sets could easily have a leading zero).

Here's my pattern:

var regcheck = /^([0-9]{4})$/;

  if(!regcheck.test(SSI_GetValue("Q10c_number1")))
  {
  strErrorMessage = "Your membership number consists of 16 digits. No letters or spaces. Please enter in the pattern provided.";
  }