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@CALCTEXT(if([sui]='1',[today],'')) This says if the "sui" field response is "Yes", pipe the value from the "Today" field, otherwise, leave blank.

Reference

the Add branching logic for the field and value as an if/then else statement[sui]='1'   This says if field equals 1, pipe the value from the date_field to the 2^nd date field, otherwise leave it blankto show or hide the field based on your needs. Here, we display the field is "Yes" is chosen for the "sui" field.

More information on using  CALCTEXT and other Conditional Logic can be found on the Help & FAQ page in REDCap

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