How can I program the selection options of the popupmenu?

I want to read a xls File in Matlab and give the User of my GUI the possibility, to choose an option depending on the data from my xls File. So the selction options of the popupmenu have to be changed. Is that possible and how can I do it?

Example:

List from xls-File:

1. green
2. blue
3. red

this are then the options of my popupmenu.

But if the List contains

1. green
2. blue
3. red
4. yellow

yellow should be also an option of the popupmenu.

[Adam]

You cabn edit the 'string' property of a uicontrol (which is what I assume you are using as a popumenu) whenever you want.

[Jan]

@Adam: This is the perfect answer already. I hestitate to post "Simply set the 'String' property of the popup menu" as my answer.