I'm aiming to have Ampscript on a Cloudpage decrement a value in a specific data extension field whenever the page loads. Eventually there will be further logic to determine which of two values to change, but as a proof-of-concept/test I'm just trying to reduce both. Currently my test page is throwing an internal server error and fails to load. The full code is below:

<!doctype html>
<meta charset="utf-8">
<meta name="description" content="">
<meta name="viewport" content="width=device-width, initial-scale=1">
Var @ontrade, @email, @otdec, @emdec, @update1, @update2

Set @ontrade = Lookup('GB_Test_Kit_Count', 'Count', 'Type', 'ontrade')
Set @email = Lookup('GB_Test_Kit_Count', 'Count', 'Type', 'email')
Set @otdec = Add(@ontrade,-1)
Set @emdec = Add(@email,-1)

Set @update1 = UpdateData(

Set @update2 = UpdateData(

The data extension is named GB_Test_Kit_Count. It has two columns, 'Type' and 'Count' and two records {ontrade, 50} and {email, 100}.

I'm guessing I've just screwed up the syntax somewhere, but I can't spot the problem.

1 Answer 1


The problematic part is:

Set @otdec = @ontrade-1
Set @emdec = @email-1

You can use Subtract or Add like:

Set @otdec = Add(@ontrade,-1)
Set @emdec = Add(@email,-1)

The documentation:



  • Made that change, but I'm still getting the same error. Jan 17, 2019 at 9:38
  • Are you doing it on the same page or on a new page? In other words, do you see "placeholder" text when you preview the page before publishing? Jan 17, 2019 at 9:40
  • The preview doesn't render at all. It's just a grey screen with an endless loading icon. Jan 17, 2019 at 9:42
  • It works on my end, the only possible solution that I think is trying the code in a new page because when you are working on the same page, because of cache issues, you still see the error. Jan 17, 2019 at 9:44
  • Even when I copy the code to a new page it doesn't work. I thought it might be because the capitalization was different on the column names between the DE and the code, but I fixed that and it hasn't helped. Jan 17, 2019 at 14:11

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