The only way that i could think of was to set "If" condition on first screen button "Login" but still not working...
I tried to set 2 "If" conditions on this button as follows:
If(!IsBlank(LookUp(UserTimeApp, Title=UserField.Text And Password=PassField.Text).Title), Navigate(MainScreen), UpdateContext({ShowForgetMessage:true}));
If(LookUp('Time Records', varNewItem.ID = ID, 'Active Session' = true), Navigate(Parent); UpdateContext({ShowPopupSession: true}), Navigate(MainScreen)); First line is checking in a SharePoint List for the user and password and if these are not correct it displays an error saying user or pass incorrect ... and if they are correct it goes to MainScreen.
Then I used the second "If" to check in SharePoint List for ID and "Active session" to be "true" and if these 2 conditions are true it should popup a 'warning info' saying that there is already a session running

but it doesn't work...
What am i doing wrong ?
Any help will be very usefull...
Thank you !