Hi @andyw2 ,
Do you want to calculate the time that you worked?
Could you tell me the time unit that you want? minutes/hours?
I assume that you want to count time by minutes.
1)If you use 2 textboxes to enter time: (enter time like 0800,1600)
set the label's Text:
"working time:"&DateDiff(Time(Value(Left(TextInput1.Text,2)),Value(Right(TextInput1.Text,2)),0),Time(Value(Left(TextInput2.Text,2)),Value(Right(TextInput2.Text,2)),0),Minutes)
2)If you use 4 textboxes to enter time: (enter hour in textinput1,textinput3; enter minutes in textinput2, textinput4)
set the label's Text:
"working time:"&DateDiff(Time(Value(TextInput1.Text),Value(TextInput2.Text),0),Time(Value(TextInput3.Text),Value(TextInput4.Text),0),Minutes)
3)If you use four drop downs to choose time(choose hour in drop down1, drop down3;choose time in drop down2, drop down4)
I more suggest you use this way because it could avoid entering invalid symbol.
Set drop down1 and drop down3 's Items:
[1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24]
Set drop down2 and drop down4 's Items:
[1,2,3,4,5,.....,60]
Set the label's Text:
"working time:"&DateDiff(Time(Dropdown1.Selected.Value,Dropdown2.Selected.Value,0),Time(Dropdown3.Selected.Value,Dropdown4.Selected.Value,0),Minutes)

Best regards,