Well, you can only combine them into one field by changing the data source
(or the query used to get the data).

To display them, all you need is

{ MERGEFIELD Stretnum } { MERGEFIELD Stretnam }

To combine them into a single /thing/ that you can re-use, you can use

{ SET myfield "{ MERGEFIELD Stretnum } { MERGEFIELD Stretnam }" }

then e.g.

{ REF myfield }

If you need to test the combined fields in an IF or COMPARE field, you can
then either use

{ IF "{ MERGEFIELD Stretnum } { MERGEFIELD Stretnam }" = "something"
"true" "false" }

or

{ IF "{ REF myfield }" = "something" "true" "false" }

Peter Jamieson

There is no reason to combine them into one merge field.  Just insert the
merge fields in the configuration that you want them.  That is with a space
between.

If you really want to combine them, open the datasouce in Excel and then use
a formula in Excel to combine them.