To do this I modified the InitValue() method within the smmActivities Data Source:
Forms > smmActivities > DataSources > smmActivities > Methods > InitValue
To do it I had to make sure that the element that was calling the form was the smmBusRelTable, then I assigned the element record to my smmBusRelTable variable. Finally, upon checking the validity of the record, I assigned the busRelTable.BusRelAccount to the busRelAccount in the smmActivities table.
The code is as follows:
THE FOLLOWING CODE GOES INTO THE FORM INIT METHOD
if (element.args().dataset() == tablenum(smmBusRelTable))
busRelTable = element.args().record();
This Goes in the smmActivities data source initvalue().
smmActivities.smmBusRelAccount = busRelTable.BusRelAccount;