EditText or label and float value

Hi ,
I 've used many years basic4ppc, but now i 'am using basic4android.
Sorry for this "basic" question, but after "But_Calcul_click action",
the result is always wrong.
I think that i have forget something....

Sub But_Calcul_Click

Dim temp As Float
Dim press As Float
Dim ktpresult As Float

TFtemp.Text= temp
TFpress.Text= press
ktpresult=(293.2/(273.2+temp))*(press/1013)
lblKTP.Text=ktpresult

End Sub

Could you help me?
thanks.