Using TextBoxes to Subtract a constant value from another TextBox

**Gal403** · 02-24-2015, 11:26 PM

Hello,

I'm looking for ideas on how I might go about coding a subtraction procedure. I have four textboxes. Textbox1 has a value of 100. Textboxes2-4 are zero. If I enter a value in either textboxes2-4 that value is subtracted from Textbox1. There is a limit. Textbox1 must never be less than 0. The user can either receive a MessageBox or further entry is prohibited. I would prefer a MessageBox alert.

I have attached a Userform1 as reference. Book1.xlsm

Thank you in advance.

Gal.

**Leith Ross** · 02-25-2015, 04:06 AM

Hello Gal403,

The code shown for the UserForm has been tested. Delete any code in the UserForm and paste this code in it's place.

UserForm Code

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**Gal403** · 02-25-2015, 04:23 AM

Thank you very much Leith! I was able to come up with my own an hour ago but found my coding awkward. I really like yours and it's doing exactly what I need so I'm going to use it although its over head. Question: What is happening here when code this "Function ZeroValueCheck(ByRef Ctrl As Control) As Boolean" ?

Many Thanks. Sincerely,
Gal

**Leith Ross** · 02-25-2015, 12:43 PM

Hello gal,

The ZeroValueCheck passes a reference to the calling object using the argument variable Ctrl. In your code, the function is called by TextBox2, TextBox3, or TextBox4. When the function is called it will sum the values of TextBox2, TextBox3, and TextBox4. This sum is then subtracted from the initial value of 100.

The difference is checked if it is below zero. If true then user is notified the result is less than zero with a message box. The text box that Ctrl refers to is set to zero, the cursor is placed at the start, and the zero is highlighted. ZeroValueCheck returns true.

The TextBox_Exit event has an argument Cancel. Setting this to true will prevent the cursor from moving to the next control on the UserForm and allowing the user to re-enter the value.