Hi,
I have a field in a table that is returning null

When i pass this null variable to a function which obviously expects something, i get an error.
How can i check null in my variable and replace it with a value ""

Is the recordset returning the literal term "null" or is it just empty?

Before your function you can perform a check for the literal "null"
If recordset("source")="Null" Then
variable=""
End If

This might help to. The isNull function returns True or False if the source is null or empty. Im not real clear on the details. At any rate, this site is a good resource.
http://www.w3schools.com/vbscript/func_isnull.asp