Variable Column Names

I am writing a stored procedure in which I have a query that selects the Headings of Columns from another table...
I want to then create a loop that will contain a variable with the value of the column heading and then set the column to a value of NULL...

Is there any way to accomplish this???

I thought about placing these values into a temp table...

This is what I have so far...

Declare @QueryX nvarchar(500)
Declare @FieldName varchar(20)

Create Table #UpdateRejDoc
(
Abbreviation varchar(20)
)
Insert into #UpdateRejDoc
Select Abbreviation
From tbl_Titles
left JOIN tbl_TitleRouting on tbl_Titles.Title_ID = tbl_TitleRouting.Title_ID
Where tbl_TitleRouting.Application_ID = @Application_ID
While Exists (Select Abbreviation from #UpdateRejDoc)
Begin

Set @QueryX = 'Update DBLandfillUser.tbl_ObjectApprovals' +
'@AppName + Set @FieldName = null Where object_id =' + Cast(@object_id as VarChar(20))
End