validation within xml

[pip12345]

Can anyone tell help me...
We have a cms that is xsl/xml based.
We have a form that has a text area that should only allow numbers.
What do I have to add to the xml to allow 'only' numbers and not any other characters?

We have some nodes in our xml called <FieldRules> where we can prompt if inputted information is incorrect.

Any help would be really appreciated.
thanks

 

[pip12345]

The xml that I'd like to change to to check for numbers only... no other type of characters allowed.
If date is a required field I added this field rules snippet.... but I want to change this so that I check & allow numbers only:

<FieldRules>
<PSXFieldValidationRules maxErrorsToStop="10" name="validDateTime">
<PSXRule boolean="and">
<PSXConditional id="1">
<variable>
<PSXSingleHtmlParameter id="0">
<name>sys_????date</name>
</PSXSingleHtmlParameter>
</variable>
<operator>LIKE</operator>
<value>
<PSXTextLiteral id="0">
<text>____-__-__%</text>
</PSXTextLiteral>
</value>
<boolean>AND</boolean>
</PSXConditional>
</PSXRule>
<PSXApplyWhen ifFieldEmpty="yes">
<PSXRule boolean="and">
<PSXConditional id="2">
<variable>
<PSXTextLiteral id="0">
<text>1</text>
</PSXTextLiteral>
</variable>
<operator>=</operator>
<value>
<PSXTextLiteral id="0">
<text>1</text>
</PSXTextLiteral>
</value>
<boolean>AND</boolean>
</PSXConditional>
</PSXRule>
</PSXApplyWhen>
<ErrorMessage>
<PSXDisplayText>This field must be a valid date and time in the format 2003-09-28 or 2003-09-28 12:00:00</PSXDisplayText>
</ErrorMessage>
</PSXFieldValidationRules>
</FieldRules>