On workbook_Open Find and replace text in VBE

[Excelnoub]

I know and search for the “Ron” coding but I don’t quiet know how to change it to my needs.

I have the code for the “Run Once” and would need to incorporate the following:

I have in all of my sheets the text “631” this will always be there as this is mine.
I need that when a user starts up my workbook, that I have assigned to him/her, that the Run Once code pops up and ask the user to identify his code (That they will already have on hand) and once that input is made to look in all sheets, replace the 631 to there number then delete the Run Once code.

Sheets (in VBE mode) I have codes that refers to "if...then add "631" to activecell.row..."

Is this possible?

Could someone help me get started, even with site with pre-made examples?