Please next time provide DDL and INSERTs like this:

CREATE TABLE #Building_Information (

Building_Name VARCHAR(50)

,Subnet VARCHAR(15)

);

INSERT INTO #Building_Information (Building_Name, Subnet)

VALUES ('Building 1', '192.168.1.%'),

('Building 2', '192.168.2.%'),

('Building 3', '192.168.3.%')

SELECT * FROM #Building_Information

CREATE TABLE #Device_Information (

DeviceNum VARCHAR(50)

,IP_Address VARCHAR(15)

);

INSERT INTO #Device_Information (DeviceNum, IP_Address)

VALUES ('Device1', '192.168.1.2'),

('Device2', '192.168.1.3'),

('Device3', '192.168.2.2'),

('Device4', '192.168.3.1'),

('Device5', '192.168.3.2'),

('Device6', '192.168.3.3')

SELECT * FROM #Device_Information

Now what do you mean by "multiple value pass"? What is the value of @Subnet when error occures?