This can be achieived by giving visibility to the open page button.
Create a boolean variable and use this variable to hide/display open page button.
Initially set this boolean to false.
Connect on change microflow for the textbox field, in the microflow, check the given string matches with entity attribute and if matches change this boolean value to true else keep it as false.
Display button only when boolean value is true.
This way you can acheive it
Create a boolean variable and use this variable to hide/display open page button, in that set boolean value as a false in a visibility of page.