You can try rebuilding your dashboard so you only drag one field onto the view.
Assuming you're using a parameter (I'll call this [user selection]), build a calculated field off of the parameter.
If [user selection] = "A Values" then [A Values]
elseif [user selection] = "B Values" then [B values]
If that doesn't work, your data is probably architected differently than I expected. Would you be able to upload your dashboard with dummy data perhaps?