How to setup Rule or Validation at L2 level of Cost code per commit in Payment Application

Hello,

I want to setup a rule or validation in Payment application BP which is "Invoice amount cannot exceed contract value" but this check should be done at L2 Level.

Eg - cost code = 0X.L1X.L2X.L3X

I want to calculate total contract amount at L2X, and if user is creating invoice greater than this amount then it should trigger an error.

Payment application BP does not allow Advanced Formula or QBDE, so it is hard to do the calculation on the form to create a validation.

I tried to put the below Rule, this check is at L3 Level, there is no way to define L2 Level codes.