If MyList contains 3 values (1,2,3), then the formula =IF(A1="",MyList,"")
in B1 of the "other" sheet returns 1 (first value of MyList) if A1 = "". But
it's not possible to choose a value from MyList. Besides, the OP wants to
input actual values in the cells which if s/he does would overwrite any
formulas. :)