Hi,
Here is the a way to do it in the rules, I used all xsl functions available in the Infopath designer, Probably this is not the best way but this is the one which worked for me
concat(translate(substring(., 1, 1), "qwertyuioplkjhgfdsazxcvbnm", "QWERTYUIOPLKJHGFDSAZXCVBNM"), substring(., 2, string-length(.)))
Agni
InfoPathDev India