Complicated IF - Subtracting from a field value

Ok. I want to have users put in their extension which is 6 digits long into a text field value.

When I pull that value I want to have an IF statement saying:

If the extension starts with the digits "11" output only the last 5 digits of the extention.

If the extension starts with the digits "10" output only the last 4 digits of the extension.

So all six digits are stored as a field value, but when I go to pull it to use it in a code I want it to output the last five digits if the six digits start with "11", or output the last four digits if the sex digits start with 10.

Is this possible???

So 2 questions really. Can I use something like wildcard stars "*" in order to identify whats in the field, like "[cb:if cb_field="10***"]" then output the last 4 digits.

And how to I subtract from a field value. Can I tell it to null characters in a field value or not display them?

IF substitutions have no way of counting the characters of a field value. You'll need to use CB Query Field to query for the field, count its characters, and output that as a SELECT query. The query field would then display the character count of that field instead of its value and you can then use that in your IF statement.

And how to I subtract from a field value. Can I tell it to null characters in a field value or not display them?

Same method as above, you'll need query field to do it.