reg difference between fields

Hi Team,

I am attempting to perform Summation of values of a text field in a detail, and I am attempting to compare the summation value and another field in another detail.

For Example.

Here I want to compare the sum on column assigned number field and the number of vacancies.if the sum on column assigned number exceeds the number of vacancies, then it should show a prompt.

Sum on column assigned number is the summation of the Assigned number.

Can u please tell me the procedure how to do this.

Hoping for a positive reply.

Regards,

Manikanta.