I have a table called Remote_Item with some records like
Code fBaseBOMGID Description
64167 C5F2EA4A-A374-464B-A001-BBBCA2EAFF8D Ear Plugs (5 Pairs)
64082 Null Ear Defenders
27940 9CF5E211-9A1F-42EA-B26E-C6693CED200D EAR PROTECTOR
93404 Null Folding Ear Defenders
26564 7959E6AA-2E52-415E-B6FB-64D6CA2EA280 SIGILL SPRAY ZINC
45589 A7859F70-453B-4F0B-BDBD-339A44488149 BOLT CUTTERS CRV 900mm
45885 4D396E23-EFE3-43C8-8E2A-090AE8704329 BOLT CUTTERS CRV 750mm
45876 868A057E-C43C-4B5C-B69D-D33C6ACF69D5 BOLT CUTTERS CRV 600mm
45869 Null BOLT CUTTERS CRV 450mm
45852 D3A74BBC-F947-4583-952D-D8E5FC89C40D BOLT CUTTERS CRV 350mm

Code = String
fCodeGID = unique identifier
Description = String
I create a loop so I can read these records and add them into another table.
Inside loop I build the insert string

Dim NewString AS String
NewString = "INSERT INTO LOCAL_Item VALUES (" & "'" & Code & "', '" & fBaseBOMGID & "', '" & Description & "'")

When the loop run working fine when all fields have data but I get error when turns to read a null value…

For example.
I read the first line and sting become like…

INSERT INTO LOCAL_Item VALUES ('64167', 'C5F2EA4A-A374-464B-A001-BBBCA2EAFF8D', 'Ear Plugs (5 Pairs)')
Working fine….

When I read the second line the string become

INSERT INTO LOCAL_Item VALUES ('64082', 'Null', 'Ear Defenders')
And I get error for Null value.

I try to use isnull function but I get the error
Conversion failed when converting from a character string to uniqueidentifier.

How I can solve it?

Thank you.