DATEADD Function Not Working

Hi,

I am having all sorts of troubles for something that should be easy.

I have a date column, and i simply want to add the number of months shown in another column to the original date.

The Date is in a table called X_Services, the Additional months i want to add is from a related table called "Promo_Months".

In the table X_Services i have the promo_months value show via the related function. Not sure if this is what's causing the issue.

I am using the DATEADD function to no avail, can anyone shed some light on how to successfully achieve this.

I did this and got the result on one occassion, but mysteriously only where the additional months value of 2 was shown .. the rest didn't show?