Macro To Rename Files In A Folder

Macro to rename files

I have following problem, discribed also in the link above.

I need a vba code to

- choose a folder instead of a file
- find all the files in the chosen folder with name that starts with "sz" and end with "_d"
- rename those files by replacing the first 5 numbers that follow sz with 5 different numbers that the user can choose e.g. through a user form.

I imagine the user to open the excel file, click on a form thats linked to a macro. The macro will call a userform and ask the user to choose the folder and type in a textbox the 5 new numbers.

I need the code that will be pasted behind the "OK" button in the userform.

Is this possible with vba?

Here a code i found in the link mentioned above, that i have applied and works - but needs to be modified to meet my needs:
Sub GetImportFileName()

Dim Filt As String
Dim FilterIndex As Integer
Dim Title As String
Dim FileName As Variant
Dim newname As String

[Code].....