Conditional Field

The questionnaire starts with a dropdown selection and for most selections, the question set doesn't change, however, for a few selections there will be a change of field.

Is there a way to do this in conditional?

I've no idea what you're asking. You want the options available in a dropdown to change based off some sort of conditions? or you want to show/hide questions based off your selection?

Sorry, I wasn't very clear. Okay, for example,

I have a dropdown with 10 choices,
7 of those choices nothing changes

If any of the other 3 are selected
one field is hidden and a different field is shown

The field I'm adding is there a way to set the condition based on those 3 possible selections?

i.e. If any equal to = choice7, choice8, choice9, hide field 3 and show field 4

Ignore me, I can affect the changes needed using PHP.

The field I'm adding is there a way to set the condition based on those 3 possible selections?

Yes, that's what the Contains and In operators are for. So if you want to check if a single select field has a value in a list of values you'd use the below.

Operator: Is In
Delimiter: ,
Value: one,two,three,four

Value would just be your comma list of values you want to match. Contains works by splitting the fields value while In works by splitting the condition value.