VBA Test For Valid Number Format

Hello Everyone,
I am looking for a function that when passed a number format as a string (e.g. "mm/dd/yyyy") returns True or False depending on whether the string is indeed a valid number format.  Obviously "mm/dd/yyyy" is valid but "1.1.2..3kklksjlkj" is not.  Does anyone have this already written up?   I'm assuming this will require the use of regular expressions and I have never swam in that end of the pool.

Many thanks!
Kyle

P.S.  Please do not post solutions using error checking.  I know that is an option.
LVL 12
kgerbChief EngineerAsked:
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Shahid ThaikaSole ProprietorCommented:
In VBA, you can use in-built functions such as...

IsNumeric("666")

or

IsDate("08/22/1985")

However, it will only work with proper formatting. i.e. use of ' / '.

If your text contains ' . ' due to some reason, you can do something like...

IsDate(Replace("08.22.1985", ".", "/"))
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aikimarkCommented:
valid number format
The different format string options depend on the data being formatted.  Your first example was not a number format, rather a date format.  Please explain your problem in greater detail.
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aikimarkCommented:
"1.1.2..3kklksjlkj" is not
Tested this 'not valid' format string In the immediate window of a VBA application and got a result with no error message.
?format(789,"1.1.2..3kklksjlkj")
1789.1.2..3kklksjlkj

Open in new window

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kgerbChief EngineerAuthor Commented:
Hi Mark,
Thanks for your comment.  In this particular instance I am dealing with dates.  I should have been more specific in my original post.  You are correct, running this from the immediate window does not throw an error...
?Format("1/1/2000","1.1.2..3kklksjlkj")
136526.1.2..3kklksjlkj

Open in new window

However, entering this as a custom format in the Format Cells dialogue does produce an error.

At any rate, my little project is attached.  It's a simple calendar add-in that will let the user graphically pick a date and then enter it into the selected cell.  There is a text box to control the date format.  My goal is to validate the text entered into that box before I attempt to modify the cell format and write the date to the sheet.  Thus, the need to test a text string as being a valid date format.  Currently, I'm using Shahid's solution.  If I need to go with this I can, but I was hoping to gain a little more understanding of what is allowed and what it not.

Thanks,
Kyle
Calendar.xlam
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aikimarkCommented:
use the IsDate() function
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kgerbChief EngineerAuthor Commented:
Thanks Shahid!
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