Infopath 2007 field rules configuration

[v2win]

I am creating a form which contains a radio button field prompting for a
'Yes' or 'No' response. I would like to require the adjacent text field to
be set to require that it cannot be blank if the result in the preceding
radio button field is 1 (i.e, 'Yes'). Is there a way to link the result in
the radio button to the 'Cannot be blank' attribute in the associated text
field? I do not want to require an entry in the text field when the
preceding response is 2 (i.e., 'No')

Thanks