How do I export to excel limiting it to a certain week of submission?

You can use filter your data while exporting to excel.

For that:

    1) Select to your form you want to export

    2) Click "View Submissions" in More options

    3) Click settings (gear) icon below Edit

    4) You can select time frame

    5) Finally, you export the form as excel or another format.

For more information:

https://www.jotform.com/help/281-How-to-Use-Visual-Report-Filters

Hello @BonaFoodieCafe,

In addition to what @brkn has already suggested, here is a screen shot for your convenience:

Related guide: How-to-View-Form-Submissions

If you need any further assistance, please let us know.