NumberFormat in custom A/P Forms- cannot find documentation to format output

Hello,

I am trying to format the output on an A/P check using "NumberFormat", but I cannot figure out how the parameters work. The pre-loaded formats look like this:

Phone
!\(999\)\ 000\-0000;0;

Social Security Number
000\-00\-0000;0;

Zip
00000;0;

Zip+4
00000\-9999;0;

What I would like to do specifically is:

  • Format Check Number with leading zeroes
  • Add a character (always the same character) before and after the check number

So, if the check number is 1234, the output should be: x001234x

Thank you in advance for any assistance.