MKTO form allows text to be added into Number of Employees field - how to prevent

[Anonymous]

We're using a standard SFDC, Number of Employees on a Marketo registration form.  The field in SFDC is defined as an Integer, 8 characters long.  The field definition in Marketo is the same.

However, on the Marketo form, the field can only be chosen as Text, Text Area, Select, Check Box, Radio Button, Hidden. If you choose Text, then someone can enter text into the Number of Employees field and submit the form (i.e. Number of Employees = blah-blah).  Is there any way to force numbers to be entered into that field?  (without having to add even more custom javascript to the MKTO landing page)

Thanks in advance for any advice.

[Anonymous]

I don't think there is a way to accomplish this without additional Javascript/jQuery.  Here is an article with more information in regards to adding custom validation to a Marketo form before submitting it: http://community.marketo.com/MarketoArticle?id=kA050000000KyxoCAC