I've searched and searched and I must be a complete idiot because I cannot get MS Word's wildcards to work properly. (And I'm quite good with Word. Honest.)

I want to replace hyphens that are used to show negative numbers, and replace them with en-dashes.

So, for example, I need -2.1 to become –2.1.

So, in "Find" (with wildcards checked) I've entered:

-[0-9]

This works perfectly to find what I'm looking for.

In "Replace" I typed (with wildcards checked):

–\1

This is obviously wrong, since it results in the error message:
"The replace with text contains a group number which is out of range."

I would be so grateful if someone could help me fix this. I'm using Word 2011 (Mac).