How to undo && variable substitution

Hello

I have the following question:

I have a query with many unions:

select a from table where column='&&param'

union

select a from table2 where column='&&param'

.........................................................................

select a from table10 where column='&&param'

I'm using && otherwise SQL Developer will ask me 10 times to enter value for &&param.

Now I want to run for a different parameter. How do I make SQL Developer to prompt me again for variable value?