Use a variable outside of an if/case statement vb.net

I am working in vb.net visual studio express with an sql back end. I have a very long few SQL commands and I need to change a section of the sql command dependent on a number being generated from a textbox. I can either re-write 150 lines of code multiple times to handle the situation or somehow carry a variable down to it outside of an IF statement. Here is what I mean.

If textbox.text = "5" then

    Dim string = "Some text to be used in an sql statement"

Elseif textbox.text = "6" then

    Dim string = "Some other text to be used in an sql statement"

End if (Please note there are more than 2 examples)

Using comm1 as new sqlcommand ("blah blah blah " & String & " blah blah blah", conn1)

So considering the "& String & is outside of my if statement it means that it is not recognized being outside of the if statement. However I dont want to re-write 150 lines of code multiple times so I need a way to carry that string function down to it. Can i do this with the if statement or a case statement?