strfrm = ""
for i=1 to n
x(i) = ...
y(i) = ...
z(i) = ...
strfrm = strfrm + str( x(i) + "," + y(i)+ "," + z(i) )
If i < n Then
strfrm = strfrm + ";"
End If
Next

[code]
n=3
strfrm = “”
for i=1 to n
x(i) =gha(i)*trigo.rad
y(i) =dec(i)*trigo.rad
z(i) =ht(i)*trigo.rad
strfrm =strfrm + str( str(x(i)) + “,” + str(y(i))+ “,” + str(z(i)) )
If i < n Then
strfrm = strfrm + “;”
End If
Next

system.debugLog " strfrm : " + strfrm[/code]

Dim arr() As String
For i As Integer = 1 To n
x(i) = ...
y(i) = ...
z(i) = ...
arr.Append(Str(x(i)) + "," + Str(y(i)) + "," + Str(z(i)))
Next
Dim result As String = Join(arr, ";")
system.debugLog " result : " + result

Two codes are running properly, thanks everybody !