Set the value of a SSA field by using a different SSA field

Hi All

I just wanted to know if it is possible to set a SSA field when selecting the first SSA field in version 7.1.

I have a SSA field that is linked to company, and when the user selects the field, I want it to populate a second SSA field also linked to company with the same fieldvalue. If this is not the case but in 90% of the time it will be the user has the option to select the 2nd field value manually.

I know that something like this can be done using Ajax and the new API, but I am struggling to do it in 7.1

Oh and the fields are on a standard workflow screen, if it needs be I can move it to an asp page.

My fields are

Contractor - Company
Spur Contractor - Company


Thank you in advance

Regards

RM