Although DocuSign allows you to validate certain fields such as requiring only numbers or only letters, even with custom validation it does not allow you to validate across multiple fields. An example of when this would be helpful is when certain fields are required to add up to a certain amount (such as percentages that must add up to 100). You can use tooltips to remind the signer, but these will not stop them from completing the form if they made a mistake.
Let us say that you have three text fields and you want the signer to input values that add to 100.
First, you want to create a formula field that adds all the values together:
[X] + [Y] + [Z] = 100
By specifying within the formula that the sum equals 100, you are essentially turning this formula field into a binary expression. When the expression is true (X + Y + Z = 100), then the formula returns a value of 1. When the expression is false (X + Y + Z ≠ 100), the formula returns a value of 0. You can format this field to use white text so it will not be visible to the signer.
Note: If you want to display the added total to the signer as they enter new values, use a different formula field that has just [X] + [Y] + [Z]. This display formula should not be used in the following logic.
Next, you must turn the formula field into a trigger and create conditions that make it impossible for the signer to complete the form until the expression is made true (X + Y + Z = 100). To do so, you need to create two new required text fields, assign them the exact same data label, give them conflicting validations, and make them conditional to the formula field.
In order to create conflicting validations, you need to select Custom Validation and use a regex pattern. The example below only accepts digits 0-4 in the first field and digits 5-9 in the second.
Regex pattern 1: ^(0-4)
Regex Pattern 2: ^(5-9)
Validations also allow you to edit the error message that will appear when the wrong digit is used.
Since the fields have the same data label, any value typed in one will automatically appear in the other, making it impossible to satisfy both validations. This forces the signer to fix the issue in order to satisfy the formula expression, making the conflicting fields disappear and allowing them to complete the form.
Important Note: You can format the fields to have white, small text limited to 1 character, but since the fields are required the red outline will still be visible on the form.
Example:
*arrow represents conditional rule pointing from trigger to field to appear
**blue text represents custom validation