it might possibly be: diadochokinesis
eudiadochokinesis gets a couple of hits ,but from non-native sites, but the descriptions indicate that these refer to the same condition

Thank you very much !

Dorland's Illustrated Medical Dctionary
"diadochokinesia (di·ad·o·cho·ki·ne·sia) [Gr. diadocha in succession + -kinesi- + -ia] the function of arresting one motor impulse and substituting for it one that is diametrically opposite, to permit sequential alternating movements, as pronation and supination of the arm. Cf. adiadochokinesia and dysdiadochokinesia. Called also diadochocinesia."

"diadochokinesis (di·ad·o·cho·ki·ne·sis) - diadochokinesia."
http://www.mercksource.com/pp/us/cns/cns_hl_d...


The "eu" bit just means it is normal, and it's not really necessary to say so:
AHD4
"di·ad·o·cho·ki·ne·sia (d?-?d'?-k?-k?-n?'zh?, -k?-) or di·ad·o·cho·ki·ne·sis (-s?s)
n.
The normal power of alternately bringing a limb into opposite positions, as flexion and extension or pronation and supination.

di·ad·o·cho·ki·net·ic (-n?t'?k) adj.)"
http://www.answers.com/diadochokinesia&r=67

Thank you so very much !!