CBool(100 > 100) = True ??? (only sometimes).... strange

Now I understand that what the title says is not really possible, so I will explain the actual situation.

I have a variable declared as a Double, let's call it "dblTotal".
I do a loop and add the value of 10 text box's to the running total (dblTotal).
Each text box contains a number to only two decimal places (or zero).

Then I check to see if dblTotal is more or less than 100 (see below).

    If dblTotal > 100 Then
        dblDiff = dblTotal - 100      
        ValidAllocationTotal = False

    ElseIf dblTotal < 100 Then
        dblDiff = 100 - dblTotal
        ValidAllocationTotal = False

    Else
        ValidAllocationTotal = True
    End If

The problem is that on some occasions (have not been able to work out the common factor) the comparison evaluates that dblTotal is not equal to 100, but it is!

I have had this problem before using the Single data type and got around it by only using Double's, now I am getting it with the Double - arggggg!

The strange thing is, that if I was to change the code like below (cast dblTotal as a Single), it would work. However that is just a nasty hack and I am not prepared to do that. Any help would be great.

    If CSng(dblTotal) > 100 Then
        dblDiff = dblTotal - 100      
        ValidAllocationTotal = False

    ElseIf CSng(dblTotal) < 100 Then
        dblDiff = 100 - dblTotal
        ValidAllocationTotal = False

    Else
        ValidAllocationTotal = True
    End IfStart Free Trial